[SVE] Don't use LocalStackAllocation for SVE objects

I have introduced a new TargetFrameLowering query function:

  isStackIdSafeForLocalArea

that queries whether or not it is safe for objects of a given stack
id to be bundled into the local area. The default behaviour is to
always bundle regardless of the stack id, however for AArch64 this is
overriden so that it's only safe for fixed-size stack objects.
There is future work here to extend this algorithm for multiple local
areas so that SVE stack objects can be bundled together and accessed
from their own virtual base-pointer.

Differential Revision: https://reviews.llvm.org/D83859