This PR updates the tablegen emitter for command options to support a
simplified syntax to underline the mnemonic. Previously, you had to
write `${ansi.underline}<L>${ansi.normal}`, where `<L>` is the mnemonic.
This really hurt the readability of the description. With this PR, you
can write `${<L>}` instead.

Migrate LLDB TableGen backend to use const RecordKeeper.

This is a part of effort to have better const correctness in TableGen
backends:

https://discourse.llvm.org/t/psa-planned-changes-to-tablegen-getallderiveddefinitions-api-potential-downstream-breakages/81089

I think this is very helpful for reading generated `.inc` files.

This patch should allow the user to set specific auto-completion type
for their custom commands.

To do so, we had to hoist the `CompletionType` enum so the user can
access it and add a new completion type flag to the CommandScriptAdd
Command Object.

So now, the user can specify which completion type will be used with
their custom command, when they register it.

This also makes the `crashlog` custom commands use disk-file completion
type, to browse through the user file system and load the report.

Differential Revision: https://reviews.llvm.org/D152011

Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>

Refactor the command option enum values and the command argument table
to connect the two. This has two benefits:

 - We guarantee that two options that use the same argument type have
   the same accepted values.
 - We can print the enum values and their description in the help
   output. (D129707)

Differential revision: https://reviews.llvm.org/D129703

This is how it should've been and brings it more in line with
std::string_view. There should be no functional change here.

This is mostly mechanical from a custom clang-tidy check, with a lot of
manual fixups. It uncovers a lot of minor inefficiencies.

This doesn't actually modify StringRef yet, I'll do that in a follow-up.

Instead of polluting the LLDBTableGenBackends header with helpers used
by both emitters, move them into a separate files.

llvm-svn: 367377

This moves the std::map typedef into the header so it can be reused by
all the emitter implementations.

llvm-svn: 367363

Splitting the different logic is cleaner and we it will be easier
to implement the enum emitting (which otherwise would have to
reimplement the Record parsing).

llvm-svn: 367207