Add support for the `low_mem_addressing_bits` and
`high_mem_addressing_bits` keys in the stop reply packet,
in addition to the existing `addressing_bits`. Same
behavior as in the qHostInfo packet.
Clean up AddressableBits so we don't need to check if
any values have been set in the object before using it
to potentially update the Process address masks.
Differential Revision: https://reviews.llvm.org/D158041
6f4a0c762f