[lldb][AArch64] Add UnpackTagsFromCoreFileSegment to MemoryTagManager

This is the first part of support for reading MTE tags from Linux
core files. The format is documented here:
https://www.kernel.org/doc/html/latest/arm64/memory-tagging-extension.html#core-dump-support

This patch adds a method to unpack from the format the core
file uses, which is different to the one chosen for GDB packets.

MemoryTagManagerAArch64MTE is not tied one OS so another OS
might choose a different format in future. However, infrastructure
to handle that would go untested until then so I've chosen not to
attempt to handle that.

Reviewed By: omjavaid

Differential Revision: https://reviews.llvm.org/D129487