[lldb/script] Improve `scripting extension list` output and filtering (#209400)

This patch improves `scripting extension list` in three ways.

First, it groups the output by `ScriptedExtension`: instead of one row
per registered plugin instance, one entry per extension is printed with
a combined `Language` field.

Second, it colorizes and visually separates the output. Each entry is
preceded by a dimmed dashed separator; field labels are printed in bold
green, the extension name value in bold cyan as a mini-heading, and
`None` usage values are dimmed, all via the same
`ansi::FormatAnsiTerminalCodes(..., use_color)` idiom
`Breakpoint::GetDescription` uses elsewhere, gracefully no-op when color
is disabled or unsupported. `ScriptedInterfaceUsages::Dump` takes an
optional `use_color` parameter so its own `API Usages:` / `Command
Interpreter Usages:` labels can match.

Third, it adds `-j`/`--json` to emit a JSON array of `{name,
description, languages, api_usages, command_interpreter_usages}` per
extension, mirroring `plugin list`'s existing `-j`. `DoExecute` now
computes the extension grouping once and branches into
`OutputJsonFormat` or `OutputTextFormat`, sharing a
`GetLanguagesForExtension` helper. It also accepts optional positional
`<extension-name>` arguments to filter the listing to specific
extensions (matched via the same case-insensitive
`ScriptInterpreter::StringToExtension` used by `scripting extension
generate`), with completion wired up via `eScriptedExtensionCompletion`.

Also fix a latent lifetime bug in the shared language-collection helper
so it owns its `std::string` values instead of holding `StringRef`s to
temporaries; the JSON path made it observable.

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