Fix warnings in class ref

[Piralein]

Fix: WARNING: Could not lex literal_block as "csharp". Highlighting skipped
(invalid comment character # instead of //)

Fix: WARNING: undefined label: class_popup_property_popup_window
the referenced member needs to reference the parent class

Fix: WARNING: undefined label: class_basis_operator_mul_vector3, ...
Operators with the same name didn't create the class ref in the operator description section.

This fix results in: WARNING: Duplicate explicit target name
Operators can have the same name and return type, which are used to create the ref identifier, resulting in duplicates.
example: class_float with vector2 and vector2i both returning vector2

This change will instead include parameter types and not return types in the identifier, but this can break external links to the operator description.
Internal should all be updated by this change. (I hope...)

[akien-mga]

Looks good! Could you squash the commits? See PR workflow for instructions.

[mhilbrunner]

LGTM, haven't tested the make_rst.py changes though

[YuriSizov]

Tried it locally and the resulting diff for RST files looks correct.

[YuriSizov]

Thanks!