[AArch64] Replace LLVM IR function attributes for PSTATE.ZA. (#79166)

Since https://github.com/ARM-software/acle/pull/276 the ACLE
defines attributes to better describe the use of a given SME state.

Previously the attributes merely described the possibility of it being
'shared' or 'preserved', whereas the new attributes have more semantics
and also describe how the data flows through the program.

For ZT0 we already had to add new LLVM IR attributes:
* aarch64_new_zt0
* aarch64_in_zt0
* aarch64_out_zt0
* aarch64_inout_zt0
* aarch64_preserves_zt0

We have now done the same for ZA, such that we add:
* aarch64_new_za       (previously `aarch64_pstate_za_new`)
* aarch64_in_za (more specific variation of `aarch64_pstate_za_shared`)
* aarch64_out_za (more specific variation of `aarch64_pstate_za_shared`)
* aarch64_inout_za (more specific variation of
`aarch64_pstate_za_shared`)
* aarch64_preserves_za (previously `aarch64_pstate_za_shared,
aarch64_pstate_za_preserved`)

This explicitly removes 'pstate' from the name, because with SME2 and
the new ACLE attributes there is a difference between "sharing ZA"
(sharing
the ZA matrix register with the caller) and "sharing PSTATE.ZA" (sharing
either the ZA or ZT0 register, both part of PSTATE.ZA with the caller).