[lldb][AArch64] Add class for managing memory tags
This adds the MemoryTagManager class and a specialisation
of that class for AArch64 MTE tags. It provides a generic
interface for various tagging operations.
Adding/removing tags, diffing tagged pointers, etc.
Later patches will use this manager to handle memory tags
in generic code in both lldb and lldb-server.
Since it will be used in both, the base class header is in
(MemoryRegionInfo is another example of this pattern)
Reviewed By: omjavaid
Differential Revision: https://reviews.llvm.org/D97281