Cranelift: Avoid string conversion for TargetIsa on every function with the incremental cache

[bjorn3]

Feature

Avoid the string conversions in

wasmtime/cranelift/codegen/src/incremental_cache.rs

Lines 150 to 163 in 3632683

	impl CompileParameters {
	fn from_isa(isa: &dyn TargetIsa) -> Self {
	Self {
	isa: isa.name().to_owned(),
	triple: isa.triple().to_string(),
	flags: isa.flags().to_string(),
	isa_flags: isa
	.isa_flags()
	.into_iter()
	.map(|v| v.value_string())
	.collect(),
	}
	}
	}

that are done for every function. Either by hashing a binary representation of the TargetIsa instead or by caching the hash in TargetIsa.

Benefit

This reduces the overhead of computing the caching key, making the incremental cache a bit faster.