This variable is only read from.

This commit implements, in debugserver, the packet as discussed in the
RFC [1].

[1]:
https://discourse.llvm.org/t/rfc-a-new-vectorized-memory-read-packet/88441

This also allowed deleting unreachable code.

This code was duplicated in multiple places and a subsequent patch will
need to do it again.

Support for `qMemTags` packet in debugserver which allows usage of
LLDB's `memory tag read` on Darwin.

The qSpeedTest packet is used for experiments to determine the optimal
packet size for a given communication medium, e.g. to transfer 10MB of
memory, is it faster to send a hundred 100KB packets or ten 1MB packets.
It creates a packet of the requested size in a stack allocation, but is
not checking that its buffer is large enough for the requested size.

Change this allocation to be on heap, and impose a maximum size that can
be tested (4MB, for now).

rdar://158630250

This is a continuation of 68fd102, which did the same thing but only for
StopInfo. Using make_shared is both safer and more efficient:

- With make_shared, the object and the control block are allocated
  together, which is more efficient.
- With make_shared, the enable_shared_from_this base class is properly
  linked to the control block before the constructor finishes, so
  shared_from_this() will be safe to use (though still not recommended
  during construction).

Increase specificity by using the correct unit sizes. KBytes is an
abbreviation for kB, 1000 bytes, and the hardware industry as well as
several operating systems have now switched to using 1000 byte kBs.

If this change is acceptable, sometimes GitHub mangles merges to use the
original email of the account. $dayjob asks contributions have my work
email. Thanks!

A few files of lldb dir & few other files had duplicate headers
included. This patch removes those redundancies.

---------

Co-authored-by: Akash Agrawal <akashag@qti.qualcomm.com>