llvm_asm!() with indirects broken on LLVM 14

[durin42]

This broke at LLVM change bec726f - I've spent some time poking at it but it looks like it may require the attention of someone a little more familiar with inline assembly than me. Basically we need to explicitly emit the elementtype(TYPE) attribute for each indirect argument of an inline assembly call. That's mostly easy for outputs, but for inputs I think it's going to take a bit of a refactor to make it work.

[nikic]

@Amanieu To avoid unnecessary work, how far away are we from just deleting llvm_asm, now that asm has been stabilized?

[Amanieu]

llvm_asm! can be useful since it has some features that are not available with plain asm! such as multi-constraints and memory constraints. However I doubt anyone is actually relying on these so I'm happy to go ahead and just remove it.