[llvm] [ARM] Move MCStreamer::emitThumbFunc to ARMTargetStreamer (PR #126199)

[Peter Smith via llvm-commits]

https://github.com/smithp35 commented:

This looks fine to me. I've added some more Arm reviewers just in case.

Not sure whether anyone on the Macho/Windows side would be interested.

https://github.com/llvm/llvm-project/pull/126199