These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

Reapply "[NFC][DebugInfo][DWARF] Create new low-level dwarf library (#…
(#145959)
    
This reapplies cbf781f0bdf2f680abbe784faedeefd6f84c246e, with fixes for
the shared-library build and the unconventional sanitizer-runtime build.

Original Description:

This is the culmination of a series of changes described in [1].
    
Although somewhat large by line count, it is almost entirely mechanical,
creating a new library in DebugInfo/DWARF/LowLevel. This new library has
very minimal dependencies, allowing it to be used from more places than
the normal DebugInfo/DWARF library--in particular from MC.
    
1.
https://discourse.llvm.org/t/rfc-debuginfo-dwarf-refactor-into-to-lower-and-higher-level-libraries/86665/2

…145081)"

This reverts commit cbf781f0bdf2f680abbe784faedeefd6f84c246e.

Breaks a couple of buildbots.

This is the culmination of a series of changes described in [1].
    
Although somewhat large by line count, it is almost entirely mechanical,
creating a new library in DebugInfo/DWARF/LowLevel. This new library has
very minimal dependencies, allowing it to be used from more places than
the normal DebugInfo/DWARF library--in particular from MC.
    
I am happy to put it in another location, or to structure it differently
if that makes sense. Some have suggested in BinaryFormat, but it is not
a great fit there. But if that makes more sense to the reviewers, I can
do that.
 
Another possibility would be to use pass-through headers to allow
clients who don't care to depend only on DebugInfo/DWARF. This would be
a much less invasive change, and perhaps easier for clients. But also a
system that hides details.

Either way, I'm open.

1.
https://discourse.llvm.org/t/rfc-debuginfo-dwarf-refactor-into-to-lower-and-higher-level-libraries/86665/2

This PR is in the direction of separating Unwind table from FDE, and CIE
that depends on llvm/Object.

To separate, first the runtime dependencies have to be removed, which
this commit does that.
This is similar to
[1](https://github.com/llvm/llvm-project/pull/140096),
[2](https://github.com/llvm/llvm-project/pull/139175), and
[3](https://github.com/llvm/llvm-project/pull/139326).

CFIPrograms' most common uses are within debug frames, but it is not
their only use. For example, some assembly writers encode them by hand
into .cfi_escape directives. This PR extracts printing code for them
into its own files, which avoids the need for the main class to depend
on DWARFUnit, sections, and similar.

One in a series of NFC DebugInfo/DWARF refactoring changes to layer it
more cleanly, so that binary CFI parsing can be used from low-level
code, (such as byte strings created via .cfi_escape) without circular
dependencies. The final goal is to make a more limited dwarf library
usable from lower-level code.

More information can be found at
https://discourse.llvm.org/t/rfc-debuginfo-dwarf-refactor-into-to-lower-and-higher-level-libraries/86665

(Revised version of a previous, unreviewed, PR.)

Move all expression verification into its only client: DWARFVerifier.
Move all printing code (which was a mix of static and member functions)
into a separate class.

This is one in a series of refactoring PRs to separate dwarf
functionality into lower-level pieces usable without object files and
sections at build time. The code is already written this way via various
"if (section == nullptr)" and similar conditionals. So the functionality
itself is needed and exists, but only as a runtime feature. The goal of
these refactors is to remove the build-time dependencies, which will
allow the existing functionality to be used from lower-level parts of
the compiler. Particularly from lib/MC/.... More information at:


https://discourse.llvm.org/t/rfc-debuginfo-dwarf-refactor-into-to-lower-and-higher-level-libraries/86665

This patch transforms:

  X && *X == Y

to:

  X == Y

where X is of std::optional<T>, and Y is of T or similar.

This patch introduces support for the DWARF operation
`DW_OP_GNU_implicit_pointer `(value 0xf3) within LLVM's DWARF parsing
and expression evaluation infrastructure. This GNU extension is used to
describe the location of a variable that is itself a pointer, where the
value of this pointer is stored at an address derived from another DWARF
location expression plus a constant offset.
Motivation:
Compilers like GCC use `DW_OP_GNU_implicit_pointer `to represent the
location of certain variables.Without support for this opcode, debuggers
like LLDB (and other tools relying on LLVM's DWARF libraries) cannot
correctly resolve the location of such variables, leading to an
inability to inspect their values or an incorrect debugging experience.

Currently, DWARFDataExtractor can extract data without performing
relocations, (eg, by checking if the section pointer is null) but is
coded such that it still depends on all the relocation machinery, like
DWARFSections and similar. All at build time.

Extract most functionality into a new class, DWARFDataExtractorBase, and 
have DWARFDataExtractor add the relocation dependent pieces via CRTP.  
Add a new class, DWARFDataExtractorSimple, which does no relocation at 
all. This will allow moving DWARFDataExtractorSimple into a new lower-level, 
lighter-weight library with fewer external build-time dependencies.

This is another in a series of refactoring changes to create a new
better-layered, low-level Dwarf library that can be called from
lower-level code without circular dependencies.