Emit LLVM range metadata for call instructions

[hanna-kruppe]

Adding !range to a call instruction to communicate the possible range of the return value (analogous to !range on loads) already works in LLVM today, we just need to use it. Fixes the test case in #49572 and we already have the information anyway, so it's a cheap and easy win. cc @eddyb

[nox]

I'll try to implement that.

[hanna-kruppe]

@nox noticed that this can't actually help with NonZeroU32::get (#49572) because the return type there is plain old u32 🤦‍♂️ But it still helps functions that return fieldless enums, or more generally enums that get packed into a single scalar (but not scalar pairs).