Configure command line arguments in Android and WASM

[DJMcNab]

Primarily, the two new environment variables are very useful:

1. VELLO_STATIC_LOG allows configuring logging for Android (equivalent to RUST_LOG, but at compile time)
2. VELLO_STATIC_ARGS allows configuring the command line arguments

For example,

VELLO_STATIC_LOG="with_winit=debug,vello::wgpu_engine=debug" VELLO_STATIC_ARGS="--test-scenes --scene 2 --use-cpu" cargo apk run -p with_winit --lib --release

would have debug level logging in with_winit and the wgpu_engine module, and start at the third test scene, using the CPU shaders

[waywardmonkeys]

Since this is adding a dependency on log, this might be a good time (in a separate issue?) to discuss using tracing instead ... There's an open issue about winit moving to tracing as well.

[DJMcNab]

Possibly - we already depend on both in with_winit and with_bevy. In the main vello crate, I think we depend on log already, but not tracing directly.

[xorgy]

I like it.