Generate Orchestration script documentation

[Naros]

Description

A developer should be able to search for an Orchestration by its filename, much like an unnamed GDScript class and to view its associated documentation like other script languages, i.e.:

Implementation ideas

This requires four changes:

1. OScriptLanguage::get_type() should return OScript::get_class_static() rather than Orchestrator.
2. The language's icon should be registered with OScript::get_class_static() in plugin.cpp.
3. OScriptLanguage::_supports_documentation() should return true.
4. OScript::_get_documentation() should return the documentation metadata.

[Naros]

A few extra noteworthy points:

• The OScript / Orchestration should support storing a brief & long description.
• The OScript / Orchestration should support several flags: Deprecated & Experimental
• The OScriptFunction should support a description field.
• The OScriptSignal should support a description field.
• The PoC work in script_docdata.h / script_docdata.cpp requires amending for serializing method default values.

[Naros]

I am moving this to the Orchestrator 2.2 timeline, as this likely won't be added until Godot 4.4.