[llvm] [SPIR-V] Add vector type support for non-standard integers in G_TRUNC op (PR #198213)

[Dmitry Sidorov via llvm-commits]

https://github.com/MrSidims approved this pull request.

Thanks!
Q: This fixes G_TRUNC specifically, but widenScalarType still early-returns on vectors, so other vector ops on non-standard int element types remain un-widened. Is G_TRUNC the only op that currently reaches here with such types, or is this the first of several follow-ups? Worth a note in the description.

https://github.com/llvm/llvm-project/pull/198213