Rework of GDScript classes' documentation generation (docgen).

Changes:

• Removes docgen code & datastructures from gdscript_compiler.cpp and gdscript.cpp
• Docgen uses analyzer datatypes instead of less expressive runtime datatypes
• Enums return/parameter types docgen'd properly instead of being Variant or int. Fixes #71117
• Makes hyperlinks to unopened classes generate their documentation on-demand rather than show blank screen. Fixes #72406
• Signals parameter types are docgen'd correctly instead of being Variant
• Added same-line docstrings for variables/constants
• Show external class specifiers e.g. TileSet.CellNeighbor instead of CellNeighbor, OtherClass.Enum or InnerClass.Enum instead of just Enum
• ⚠️ ⚠️ ⚠️ Remove unnecessary class specifier path, e.g. InnerClass.Enum instead of CurrentClass.InnerClass.Enum or Inner3.Enum instead of Class.Inner1.Inner2.Inner3.Enum, when documented inside Inner2⚠️ ⚠️ ⚠️ this one might be slightly contentious ⚠️ ⚠️ ⚠️
• Created a fairly comprehensive set of gdscript files with all/most combinations of types to make sure this works properly (linked below)

Minor changes:

• Removes unused p_scroll parameter in EditorHelp::go_to_class() and p_vscr in EditorHelp::_goto_desc()
• Removed unused DocData::EnumDoc
• Normalize docstrings in EditorHelp source code

Enums and class specifiers everywhere!

Before (boooooo):

After (yaaaaaay):

Inline docstrings!

Possibly contentious class specifier prefix elimination!

(see below for gdscript class & enum types)

Notice how we are within Doc1.IC, and therefore in the highlighted areas only relevant class specifier prefixes are shown. We don't need Doc1.IC, just IC. We don't need Doc1.IC.IE or IC.IE, just IE. We don't need Doc1.IC.IIC or Doc1.IC.IIC.IIE, just IIC or IIC.IIE.

Test files!

gdscript_docgen.zip

These are the files I used to test. They are organized as follows:

1. Two outer classes, Doc1 and Doc2
2. Doc1 and Doc2 have an inner class IC, which has an inner inner class IIC.
3. Each class, outer or inner, has corresponding enums, E, IE, and IIE.
4. Doc1 and inner classes, have methods containing all combinations of accessing classes and enums I could think of, both as parameters and return types.

As far as I can tell, every type name is as I thought it made the most sense (i.e. remove prefixes which are "obvious"), and click-linking works also.