x64: handle ISA features more completely

[abrown]

This adds full boolean term support for instructions emitted in the new assembler (terms like (_64b | compat) & avx2). Despite doing more checks, this may be quicker too: instead of building up a SmallVec<InstructionSet> to compare against, this generates Rust code like the following that queries what features are available in the target via the AvailableFeatures trait:

#[must_use] // cranelift/assembler-x64/meta/src/generate/inst.rs:227
pub fn is_available(&self, features: &impl AvailableFeatures) -> bool {
    (features._64b() || features.compat()) && features.avx2() // cranelift/assembler-x64/meta/src/generate/inst.rs:232
}

With all of this in place, this PR has a large mechanical translation of all the old, incorrect feature definitions (_64b | compat | avx2) into their new, correct definitions ((_64b | compat) & avx2). I expect this will see a lot more use of this when using more instructions from AVX512, AVX10, APX, etc.

[abrown]

So this is a bit unfortunate at the moment: we've lost the ability to see why this check has failed. I mulled this over for a bit, thinking how we can get this back. One option is to have the assembler just "return the right string" through some other method which we can paste in here. But I'm leaning toward adding an Inst::features() -> Features, much like we had before, but that would return a boolean term like the one we have available at the meta level. Though this would duplicate the some of Features, it would return an enum that is more widely usable than a string while I still have all of this paged in.

Either option, "return a string" or "return a Features", is really fine at this point and I'm interested in feedback. Also, this seems like something that could get fixed up in a follow-on PR.

[abrown]

I do expect this to fail in Winch: something about how we're using -Ccranelift-has-avx2 in param_av2.wat doesn't seem to propagate the right features into the ISA flags used here:

wasmtime/winch/codegen/src/isa/x64/masm.rs

Lines 3205 to 3208 in 3c9305c

	fn ensure_has_avx2(&self) -> Result<()> {
	anyhow::ensure!(self.flags.has_avx2(), CodeGenError::UnimplementedForNoAvx2);
	Ok(())
	}