[clang] [llvm] [LLVM][SROA] Teach SROA how to "bitcast" between fixed and scalable vectors. (PR #130973)

[Paul Walker via cfe-commits]

paulwalker-arm wrote:

@pawosm-arm - I've removed the reviewers because it is not quite ready yet.  I need to investigate the potential regressions shown by the RISCV tests.

https://github.com/llvm/llvm-project/pull/130973