[AArch64][SME] Disable (SLP|Loop)Vectorizer when function may be executed in streamin...

[AArch64][SME] Disable (SLP|Loop)Vectorizer when function may be executed in streaming mode.

When the SME attributes tell that a function is or may be executed in Streaming
SVE mode, we currently need to be conservative and disable _any_ vectorization
(fixed or scalable) because the code-generator does not yet support generating
streaming-compatible code.

Scalable auto-vec will be gradually enabled in the future when we have
confidence that the loop-vectorizer won't use any SVE or NEON instructions
that are illegal in Streaming SVE mode.

Reviewed By: paulwalker-arm

Differential Revision: https://reviews.llvm.org/D135950