[llvm] [NFC][SPIRV] Move `SPIRVStripConvergenceIntrinsics` to Utils (PR #188537)

[Nathan Gauër via llvm-commits]

Keenuts wrote:

Would it be possible to to the file renaming between the SPIRVStripConvergence to StripConvergenceIntrinsics.cpp using `git mv` ? If so, we might be able to correctly identify what changed (since algo slighty changed) and keep track of history.

https://github.com/llvm/llvm-project/pull/188537