Some data members are only part of a class definition in a Debug build,
e.g. `LVObject::ID`. If `debuginfologicalview` is used as a library,
`NDEBUG` cannot be used for this purpose, as this PP macro may have a
different definition in a downstream project, which in turn triggers an
ODR violation. Fix it by
- Making `LVObject::ID` an unconditional data member.
- Making `LVObject::dump()` non-virtual. Rationale: `virtual` is not
needed (and it calls `print()`, which is virtual anyway).

Fixes #139098.

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.

Hoist out from LVDWARFReader and LVBinaryReader some generic
code, so it can be available to other readers that do not share the
binary format.

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.