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

(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

As specified in the docs,
1) raw_string_ostream is always unbuffered and
2) the underlying buffer may be used directly

( 65b13610a5226b84889b923bae884ba395ad084d for further reference )

* Don't call raw_string_ostream::flush(), which is essentially a no-op.
* Avoid unneeded calls to raw_string_ostream::str(), to avoid excess
indirection.

lldbUtility seems like a more suitable place for StreamBuffer.

Differential Revision: https://reviews.llvm.org/D157463

Differential Revision: https://reviews.llvm.org/D134817

This reverts commit 7dde94251e1c9e4634f5d51d41f2d4a191258fb3.

Because of test failures:

  lldb-shell :: SymbolFile/DWARF/x86/DW_AT_loclists_base.s
  lldb-shell :: SymbolFile/DWARF/x86/debug_loc.s
  lldb-shell :: SymbolFile/DWARF/x86/debug_loc_and_loclists.s
  lldb-shell :: SymbolFile/DWARF/x86/debug_loclists-dwo.s
  lldb-shell :: SymbolFile/DWARF/x86/debug_loclists-dwp.s
  lldb-shell :: SymbolFile/DWARF/x86/dwp.s
  lldb-shell :: SymbolFile/DWARF/x86/unused-inlined-params.test
  lldb-shell :: SymbolFile/NativePDB/inline_sites.test
  lldb-shell :: SymbolFile/NativePDB/local-variables-registers.s
  lldb-shell :: SymbolFile/NativePDB/nested-blocks-same-address.s

Differential Revision: https://reviews.llvm.org/D134817

This reverts commit d96ade00c3c96bd451c60e34a17e613cdd5fdc38.