Add `architecture` to `RustExtension`

[garysassano]

The compatiblearchitectures property is not available in RustExtension, so it always compiles for x64.

A workaround is to manually specify the architecture flag in the bundling property:

const myExtension = new RustExtension(
 this,
 "MyExtension",
 {
 manifestPath: join(
 __dirname,
 "..",
 "layers/my-extension",
 "Cargo.toml",
 ),
 bundling: { cargoLambdaFlags: ["--quiet", "--arm64"] },
 },
);

It would be more convenient to introduce an architecture property that accepts either Architecture.X86_64 (default) or Architecture.ARM_64. Setting this property would not only automatically add the --arm64 flag but also configure the layer correctly in the AWS Console:

[calavera]

That makes sense, although I would probably just call it architecture to match the option in RustFunction. This should be easy to add if you feel like opening a Pull Request with the addition.

[garysassano]

Yeah, I agree architecture is actually a better name.