[AArch64][SME] Add codegen pass to handle ZA state in arm_new_za functions.

The new pass implements the following:

* Inserts code at the start of an arm_new_za function to
    commit a lazy-save when the lazy-save mechanism is active.
* Adds a smstart intrinsic at the start of the function.
* Adds a smstop intrinsic at the end of the function.

Patch co-authored by kmclaughlin.

Differential Revision: https://reviews.llvm.org/D133896