Restructure JSImport/JSExport generators to share more code and utilize more Microsoft.Interop.SourceGeneration shared code

[jkoritzinsky]

Split out the MarshalerType/Bind logic to not run through the generators (and instead run through the generator resolver only, which allows removing the IJSMarshallingGenerator type and many of the different generator types (as most of them end up using the same logic as the primitive generator).

Update JSFunctionBinding to not use Unsafe.AsPointer to allow the source generator to use collection expressions (fixing one of the rude-edit errors in #107577 by removing the stackalloc) without depending on Roslyn implementation details.

Also use more pattern matching instead of when expressions where possible in JSGeneratorResolver to make the giant table a little more readable in my opinion.

Replat the JS generators to use the same stub generators as the LibraryImport and GeneratedComInterface source generators by using local functions to shim from the JS generator signatures (which take a buffer) to the more standard "separate arguments" format used by those generators.

This PR also adds support in Microsoft.Interop.SourceGeneration for an exception marshaller that corresponds to a different native location than the return location (to support the separate exception return from the argument return).

[jkoritzinsky]

For return values, here's the old codegen for return types (to compare against the ValidateGeneratedSourceOutput_Return test)

Old Code Gen

// JSImports.g.cs
// <auto-generated/>
unsafe partial class Foo
{
    [global::System.Diagnostics.DebuggerNonUserCode]
    public static partial global::System.Threading.Tasks.Task<int> Func()
    {
        if (__signature_Func_408569705 == null)
        {
            __signature_Func_408569705 = global::System.Runtime.InteropServices.JavaScript.JSFunctionBinding.BindJSFunction("Func", null, new global::System.Runtime.InteropServices.JavaScript.JSMarshalerType[] { global::System.Runtime.InteropServices.JavaScript.JSMarshalerType.Task(global::System.Runtime.InteropServices.JavaScript.JSMarshalerType.Int32) });
        }

        global::System.Span<global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument> __arguments_buffer = stackalloc global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument[2];
        ref global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument __arg_exception = ref __arguments_buffer[0];
        __arg_exception.Initialize();
        ref global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument __arg_return = ref __arguments_buffer[1];
        __arg_return.Initialize();
        global::System.Threading.Tasks.Task<int> __retVal;
        global::System.Runtime.InteropServices.JavaScript.JSFunctionBinding.InvokeJS(__signature_Func_408569705, __arguments_buffer);
        // UnmarshalCapture - Capture the native data into marshaller instances in case conversion to managed data throws an exception.
        __arg_return.ToManaged(out __retVal, static (ref global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument __task_result_arg, out int __task_result) =>
        {
            __task_result_arg.ToManaged(out __task_result);
        });
        return __retVal;
    }

    static global::System.Runtime.InteropServices.JavaScript.JSFunctionBinding __signature_Func_408569705;
}

// JSExports.g.cs
// <auto-generated/>
namespace System.Runtime.InteropServices.JavaScript
{
    [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute]
    unsafe class __GeneratedInitializer
    {
        [global::System.ThreadStaticAttribute]
        static bool initialized;
        [global::System.Runtime.CompilerServices.ModuleInitializerAttribute, global::System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute(global::System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicMethods | global::System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.NonPublicMethods, "System.Runtime.InteropServices.JavaScript.__GeneratedInitializer", "Console")]
        static internal void __TrimmingPreserve_()
        {
        }

        [global::System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute("__Wrapper_NetFunc_408569705", "Foo", "Console")]
        static void __Register_()
        {
            if (initialized || global::System.Runtime.InteropServices.RuntimeInformation.OSArchitecture != global::System.Runtime.InteropServices.Architecture.Wasm)
                return;
            initialized = true;
            global::System.Runtime.InteropServices.JavaScript.JSFunctionBinding.BindManagedFunction("[Console]Foo:NetFunc", 408569705, new global::System.Runtime.InteropServices.JavaScript.JSMarshalerType[] { global::System.Runtime.InteropServices.JavaScript.JSMarshalerType.Task(global::System.Runtime.InteropServices.JavaScript.JSMarshalerType.Int32) });
        }
    }
}
unsafe partial class Foo
{
    [global::System.Diagnostics.DebuggerNonUserCode]
    internal static unsafe void __Wrapper_NetFunc_408569705(global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument* __arguments_buffer)
    {
        ref global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument __arg_exception = ref __arguments_buffer[0];
        ref global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument __arg_return = ref __arguments_buffer[1];
        global::System.Threading.Tasks.Task<int> __retVal = default;
        try
        {
            __retVal = Foo.NetFunc();
            // Marshal - Convert managed data to native data.
            __arg_return.ToJS(__retVal, static (ref global::System.Runtime.InteropServices.JavaScript.JSMarshalerArgument __task_result_arg, int __task_result) =>
            {
                __task_result_arg.ToJS(__task_result);
            });
        }
        catch (global::System.Exception ex)
        {
            __arg_exception.ToJS(ex);
        }
    }
}

[jkoritzinsky]

I ran the JSImportManyArgs benchmark and I saw the following results:

main: average 71.2133ms
pr: average 68.3718ms

So, this PR is also a perf improvement for JSImport, about 3ms, which is 4% faster.

[pavelsavara]

These don't need to be assigned default

[jkoritzinsky]

As we introduce exception handling here, we initialize the variables so (in case they're touched in the exception clause) they're initialized. At the time of generating this initialization, we can't know if they'll be used, only that we are generating a try block with some exception handling.

[jkoritzinsky]

/ba-g failures are unrelated