[lldb][AArch64] Add tag packing and repetition memory tag manager

PackTags is used by to compress tags to go in the QMemTags packet
and be passed to ptrace when writing memory tags.

The behaviour of RepeatTagsForRange matches that described for QMemTags
in the GDB documentation:
https://sourceware.org/gdb/current/onlinedocs/gdb/General-Query-Packets.html#General-Query-Packets

In addition, unpacking tags with number of tags 0 now means
do not check that number of tags matches the range.
This will be used by lldb-server to unpack tags before repeating
them to fill the requested range.

Reviewed By: omjavaid

Differential Revision: https://reviews.llvm.org/D105179