chore: fix all warnings

[nyurik]

This fixes all compiler warnings. Note that __cbindgen_hack__ = "yes" is a bit weird - there is no need to make it support a value -- presence of a keyword is an indicator enough. Also, I couldn't figure out what actually sets that value.

[syrusakbary]

This feature was deprecated long ago. We shouldn't add it back

[nyurik]

You use it in

wasmer/lib/c-api/src/wasm_c_api/engine.rs

Line 258 in d431db9

#[cfg(all(feature = "compiler", any(feature = "compiler", feature = "dylib")))]

- generating compiler warning because dylib is not declared. Should it be removed there?

[syrusakbary]

This create will be deprecated (removed from the repo) very soon, we shouldn't add new features to it

[nyurik]

If the features are used in code, they should be declared in cargo.toml - otherwise its like using a variable without declaring it first - ok for some languages, but usually a bad form for Rust :) Should they be removed there, or should these be added here until then?

[syrusakbary]

Why is tracing a feature if it's not used anywhere?

[nyurik]

it is used in

wasmer/lib/sys-utils/src/memory/fd_memory/fd_mmap.rs

Line 241 in d431db9

#[cfg(feature = "tracing")]

and

wasmer/lib/sys-utils/src/memory/fd_memory/fd_mmap.rs

Line 257 in d431db9

#[cfg(feature = "tracing")]

[nyurik]

@syrusakbary thx for the quick review! The reason I added those is because you have a lot of cfg(feature = "...") that still use those features - generating warnings. IF they are deprecated, they should be removed at the same time from the code and cargo.toml, or else it is really confusing why the warnings are being generated