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.

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
```

The code dealing with DW_AT_call_line/DW_AT_call_file is in the wrong
place. The correct functions were call, but with incorrect values:
  DW_AT_call_line <-- Filename Index
  DW_AT_call_file <-- Line number

As part of the WebAssembly support work
https://github.com/llvm/llvm-project/pull/85566

The README.txt is a bit odd since it only lists issues and problems
without talking about what works. It’s also hard to read on the GitHub
web view.

- Convert to Markdown and linking to the command docs
https://llvm.org/docs/CommandGuide/llvm-debuginfo-analyzer
- Rename some left 'elf reader' to 'DWARF reader'.

As part of the WebAssembly support work
https://github.com/llvm/llvm-project/pull/82588

As the object files used in the test cases are a single object (just
produced by clang without being processed by wasm-ld), it was determined
to use .o intead of .wasm.

Update the README.txt to reflect that the tool now supports WebAssembly.

Add support for the WebAssembly binary format and be able to generate
logical views.

https://github.com/llvm/llvm-project/issues/69181

The README.txt includes information about how to build the test cases.

Originally committed in fe7a3cedf77125a6309150d85cecbc20b1a31775

Reverted in 26dd64ba9cfabe5474bb207f3b7099965f81fed7

Buildbot failures:
https://lab.llvm.org/buildbot#builders/139/builds/29663
- unittest trigger an invalid assertion.

https://lab.llvm.org/buildbot#builders/196/builds/19665
- 'has virtual functions but non-virtual destructor' warning as error.

Recommitted with fix:
- Removed the assertion.
- Added virtual destructor.

This reverts commit fe7a3cedf77125a6309150d85cecbc20b1a31775.