GDScript: Unify StringName and String

[rune-scape]

this change aims to fix #64171 by letting String and StringName be used nearly interchangeably in GDScript

registers all string methods to StringName in variant_call.cpp
-- So String methods can be used on StringNames ('&"stringname".has("str")' and vice versa)

fills in the gaps between String and StringName in variant_op.cpp
-- So '"str" in &"stringname"' works and among others

Array will silently coerce Strings and StringNames into each other when typed in any method that takes a variant input
-- So Array acts like they are almost the same type, but silently converts if inserted or anything into a typed Array
-- fixes #63965, all 4 tests return true

other functions in untyped Array will also compare Strings and StringNames
-- fixes #68918

Dictionary now compares String and StringName keys
-- which fixes #62957

lastly, the analyzer will do the same
-- So it doesn't tell you you can't assign Array[String] to Array[StringName]
and the compiler will make an exception in match statements for String and StringName, allowing comparisons
-- which fixes #60145

also added a check for StringName in a couple places (regex.cpp and scene_rpc_interface.cpp)

Notes and things to discuss:

• Array ==, <, >, etc. still do not compare Strings and StringNames as equal, not sure if this is desired?
• Dictionary ==, <, >, still DO compare String and StringName keys as equal, but only because StringNames are converted to Strings on insertion, does that make it different from Array?
• Strings and StringNames still cannot be compared using <, >, etc. in GDScript, should this be allowed?
• Variant could benefit from an is_string() method..

[MewPurPur]

I've found no functionality regression.

As one would expect, has() and in are slower (in the ballpark of 2x as slow), insofar as arrays are concerned (and not only Array[StringName] or Array[String].) To get these results, I compared the Linux Mono editor artifact with beta 5, running lots of loops on GDScript and timing it with the Time singleton.

[rune-scape]

@MewPurPur that performance diff shouldn't be the case, although i did push a new version since you tested
i think maybe the artifacts aren't production builds?
i got similar performance running this test on a production build vs master:
test_unify.zip

[rune-scape]

In order for the last check to pass, godotengine/godot-cpp#930 needs to be merged to solve ambiguous overload errors

[MewPurPur]

Fait critique, the benchmarks need something to compare to.

[Begah]

I tested this pr and it seems to 'fix' the match statement, in gd3 this worked

match node.get_name():
    "test1":
         pass
     _:
         pass

And this PR makes this code work again ( Need to do StringName("test1") for the match to work, or String(node.get_name()) without this PR)

[KoBeWi]

I didn't test, but looking at the code it also fixes #68834

[akien-mga]

Thanks!