[AsmParser] Support calling intrinsics without mangling suffix (#89172)

This adds proper support for calling intrinsics without mangling suffix
when parsing textual IR. This already worked (mostly by accident) when
only a single mangling suffix was in use.

This patch extends support to the case where the intrinsic is used with
multiple signatures, and as such multiple different intrinsic
declarations have to be inserted. The final IR will have intrinsics with
mangling suffix as usual.

Motivated by the discussion at:
https://discourse.llvm.org/t/recent-improvements-to-the-ir-parser/77366