Fix DocGen and Access for GDScript Enums

[ColinSORourke]

• Closes Enumeration Values' docstrings not shown on hover in Script Editor #113305.

Previously modules/gdscript/editor/gdscript_docgen.cpp would treat values of Named Enums identically to values of unnamed enums, and assign them all as ConstantDocs under MyClass.gd, using the values direct name as the ConstantDoc name.

// MyClass.gd
extends Node

## 1
enum {
	A = 0, ## 2
	B = 1, ## 3
}

## DocComment 4
enum NamedEnum {
	UP = 0, ## 5
	DOWN = 1, ## 6
}

## 7
enum OtherEnum {
	UP = 0, ## 8
	TOWN = 1, ## 9
	FUNK = 2, ## 10
}

Given the above code block, that would generate ConstantDoc mapping
MyClass.gd->class_docs.constants = {"A": 2, "B": 3, "UP": 5, "DOWN": 6, "UP":8, "TOWN":9, "FUNK":10}

Then, through the lookup chain, _lookup_symbol_from_base would tell the tooltip generator to look up the docs for this NamedEnum.UP under class_name "MyClass.gd".NamedEnum, symbol name "UP", causing a failure to retrieve any class docs.

This fix instead generates the unambiguous ConstantDoc mapping
MyClass.gd->class_docs.constants = {"A": 2, "B": 3, "NamedEnum.UP": 5, "NamedEnum.DOWN": 6, "OtherEnum.UP":8, "OtherEnum.TOWN":9, "OtherEnum.FUNK":10}
And also has _lookup_symbol_from_base return a more appropriate class_name and constant symbol.

[dalexeev]

This looks incorrect. A constant name (identifier) ​​can't contain a period. At the very least, this is a hack, not a desirable option.

The main problem with proper enumeration support is that the core doc system doesn't properly support scoped enumerations. Instead, all enumeration elements are put into a common constant list. Native enumeration elements cannot be repeated, but custom enumerations can have elements with the same name in multiple enumerations.

[ColinSORourke]

This PR could be changed to just have lookup return the proper class_name, but not change anything about the symbol names, and it would at least start returning the correct DocString in most cases.

That of course would create the exact ambiguous behavior you're talking about, where MyClass.gd's ClassDoc can have multiple constants with duplicate names.

Is there an alternate Symbol scheme we could employ without the period?

[dalexeev]

I don't think we can currently do anything about this ambiguity on the GDScript side. Instead, we should first change the DocData structures and so on to properly support scoped enumerations.

• See Documentation: Store enum descriptions in XML files #98233.

[ColinSORourke]

@dalexeev

Pushed an alternate solution that is more code, but employs the Enum Scope Searching already used by _get_property_help_data (which was behaving correctly even before this PR) and performs the same search in _get_constant_help_data

Does not change any of the DocData generation

[ColinSORourke]

Disregard previous comment! I gave this a little more thought and realized the existing routine could completely resolve ambiguity and be simpler without any other adjustments to DocGen. New push as of Nov.30th should be issue-free and correctly link Constants.