[llvm] [AArch64][SME2] Preserve ZT0 state around function calls (PR #76968)

[Kerry McLaughlin via llvm-commits]

kmclaughlin-arm wrote:

Closing this pull request as the following patches have been committed for handling ZT0 state based on the changes requested above:
- https://github.com/llvm/llvm-project/pull/77607
- https://github.com/llvm/llvm-project/pull/78321
- https://github.com/llvm/llvm-project/pull/78848

https://github.com/llvm/llvm-project/pull/76968