Revert "Reland "[lldb] Remove non address bits when looking up memory regions""

This reverts commit fac3f20d.

I found this has broken how we detect the last memory region in
GetMemoryRegions/"memory region" command.

When you're debugging an AArch64 system with pointer authentication,
the ABI plugin will remove the top bit from the end address of the last
user mapped area.

(lldb)
[0x0000fffffffdf000-0x0001000000000000) rw- [stack]

ABI plugin removes anything above the 48th bit (48 bit virtual addresses
by default on AArch64, leaving an address of 0.

(lldb)
[0x0000000000000000-0x0000000000400000) ---

You get back a mapping for 0 and get into an infinite loop.