Remove unused code and unnecessary function calls, optimize global
variable search.
Add more test cases.

As a preliminary to making DIL the default implementation for
 'frame var', ran check-lldb forcing 'frame var' to always use DIL, 
and discovered a few failing tests. This fixes most of them. The only
remaining failing test is TestDAP_evaluate.py, which now passes
a test case that the test says should fail (still investigating this).

Changes in this PR:
- Sets correct VariableSP, as well as returning ValueObjectSP (needed
for several watchpoint tests).
- Updates error messages, when looking up members, to match what the
rest of LLDB expects. Also update appropriate DIL tests to expect the
updated error messages.
- Updates DIL parser to look for and accept "(anonymous namespace)::" at
the front of a variable name.

This updates the DIL implementation to handle smart pointers (accessing
field members and dereferencing) in the same way the current 'frame
variable' implementation does. It also adds tests for handling smart
pointers, as well as some additional DIL tests.

Replace (questionable) header globs with an explicit argument supported
by llvm_add_library.

If we're not touching them, we don't need to do anything special to pass
them along -- with one important caveat: due to how cmake arguments
work, the implicitly passed arguments need to be specified before
arguments that we handle.

This isn't particularly nice, but the alternative is enumerating all
arguments that can be used by llvm_add_library and the macros it calls
(it also relies on implicit passing of some arguments to
llvm_process_sources).

The problem was in calling GetLoadAddress on a value in the error state,
where `ValueObject::GetLoadAddress` could end up accessing the
uninitialized "address type" by-ref return value from `GetAddressOf`.
This probably happened because each function expected the other to
initialize it.

We can guarantee initialization by turning this into a proper return
value.

I've added a test, but it only (reliably) crashes if lldb is built with
ubsan.

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>

Reapply #138551 with an xfailed test on Windows