The two variables using ManagedStatic that are exported by this
header are not actually used anywhere -- they are used through
SubCommand::getTopLevel() and SubCommand::getAll() instead.
Drop the extern declarations and the include.

Both sides here are known to be of StringRef.

It's useful to have some significant build options visible in the
version when investigating problems with a specific compiler artifact.
This makes it easy to see if assertions, expensive checks, sanitizers,
etc. are enabled when checking a compiler version.

Example config line output:
Build configuration: +unoptimized, +assertions, +asan, +ubsan

Reverts llvm/llvm-project#84990 because this causes a full rebuild after
the commit hash changes.

Include the `LLVM_REPOSITORY` and `LLVM_REVISION` in the version output
of tools using `cl::PrintVersionMessage()` such as dwarfdump and
dsymutil.

Before:

```
$ llvm-dwarfdump --version
LLVM (http://llvm.org/):
  LLVM version 19.0.0git
  Optimized build with assertions.
```

After:

```
$ llvm-dwarfdump --version
LLVM (http://llvm.org/):
  LLVM version 19.0.0git (git@github.com:llvm/llvm-project.git 8467457afc61d70e881c9817ace26356ef757733)
  Optimized build with assertions.
```

rdar://121526866

After #75679, it is no longer necessary to add the `All` pseudo
subcommand to the list of registered subcommands. The change causes the
list to contain only real subcommands, i.e. an unnamed top-level
subcommand and named ones. This simplifies the code a bit by removing
some checks for this special case.

This is a fixed version of #77041, where options of the 'All' subcommand
were not added to subcommands defined after them.

This reverts commit fb7fe49960ae053c92985f3376d85a15bbd10d1a.

The commit introduced a bug where an option with the `All' subcommand
would not be added to a category initialized after that option.