[clang] [Clang][AArch64] Change SME attributes for shared/new/preserved state. (PR #76971)

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https://github.com/rsandifo-arm commented:

Thanks for the update, looks great to me.  The only substantive comment I have is that I think a given keyword attribute must always take `(` and `)` or never take them.  It shouldn't be optional, because that risks creating parsing ambiguities, or at least non-obvious behaviour.

https://github.com/llvm/llvm-project/pull/76971