This pull request adds support for parsing the source language in both
DWARF and CodeView. Specifically,

- The `LVSourceLanguage` class is introduced to represent any supported
language by any of the debug info representations.

- Update `LVDWARFReader.cpp` and `LVCodeViewVisitor.cpp` to parse the
source language where it applies. Added a new `=Language` attribute;
`getAttributeLanguage()` is internally used to control whether this
information is being printed.

This PR was split from https://github.com/llvm/llvm-project/pull/137228
(which introduced support for `DW_TAG_module` and `DW_AT_byte_size`).

This PR improves `LVDWARFReader` by introducing handling of
`DW_AT_byte_size`. Most DWARF emitters include this attribute for types
to specify the size of an entity of the given type.

- Adds support for `DW_TAG_module` DIEs and recurse over their children.
Prior to this patch, entities hanging below `DW_TAG_module` were just
not visible. This DIE kind is commonly generated by Objective-C modules.

This patch will represent such entities, which will print as
```
[001]    {CompileUnit} '/llvm/tools/clang/test/modules/<stdin>'
[002]      {Producer} 'LLVM version 3.7.0'
           {Directory} '/llvm/tools/clang/test/modules'
           {File} '<stdin>'
[002]      {Module} 'DebugModule'
```
The minimal test case included is just the result of
```
$ llc llvm/test/DebugInfo/X86/DIModule.ll
      -accel-tables=Dwarf
      -o llvm/unittests/DebugInfo/LogicalView/Inputs/test-dwarf-clang-module.o
      -filetype=obj
```

This pull request fixes a couple of unhandled situations in DWARF input
leading to a crash. Specifically,

- If the DWARF input contains a declaration of a C variadic function
(where `...` translates to `DW_TAG_unspecified_parameters`), which is
then followed by a definition, `llvm_unreachable()` is hit in
`LVScope::addMissingElements()`. This is only visible in Debug builds.

- Parsing of instructions in `LVBinaryReader::createInstructions()` does
not check whether `Offset` lies within the `Bytes` ArrayRef. A specially
crafted DWARF input can lead to this condition.

C++20 comes with std::erase to erase a value from std::vector.  This
patch renames llvm::erase_value to llvm::erase for consistency with
C++20.

We could make llvm::erase more similar to std::erase by having it
return the number of elements removed, but I'm not doing that for now
because nobody seems to care about that in our code base.

Since there are only 50 occurrences of erase_value in our code base,
this patch replaces all of them with llvm::erase and deprecates
llvm::erase_value.

llvm-debuginfo-analyzer is a command line tool that processes debug
info contained in a binary file and produces a debug information
format agnostic “Logical View”, which is a high-level semantic
representation of the debug info, independent of the low-level
format.

The code has been divided into the following patches:

1) Interval tree
2) Driver and documentation
3) Logical elements
4) Locations and ranges
5) Select elements
6) Warning and internal options
7) Compare elements
8) ELF Reader
9) CodeView Reader

Full details:
https://discourse.llvm.org/t/llvm-dev-rfc-llvm-dva-debug-information-visual-analyzer/62570

This patch:

This is a high level summary of the changes in this patch.

CodeView Reader
- Support for CodeView/PDB.
  LVCodeViewReader, LVTypeVisitor, LVSymbolVisitor, LVLogicalVisitor

Reviewed By: psamolysov, probinson, djtodoro, zequanwu

Differential Revision: https://reviews.llvm.org/D125784

llvm-debuginfo-analyzer is a command line tool that processes debug
info contained in a binary file and produces a debug information
format agnostic “Logical View”, which is a high-level semantic
representation of the debug info, independent of the low-level
format.

The code has been divided into the following patches:

1) Interval tree
2) Driver and documentation
3) Logical elements
4) Locations and ranges
5) Select elements
6) Warning and internal options
7) Compare elements
8) ELF Reader
8a) Memory Management
9) CodeView Reader

Full details:

https://discourse.llvm.org/t/llvm-dev-rfc-llvm-dva-debug-information-visual-analyzer/62570

This patch:

This is a high level summary of the changes in this patch.

Memory Management
- Use Bump allocators for memory management.

As the logical elements are only allocated in one pass (debuginfo
parsing) and they are never manipulated/created/destroyed later,
use the SpecificBumpPtrAllocator for the memory management.

Reviewed By: dblaikie, Orlando

Differential Revision: https://reviews.llvm.org/D137933