Rename ord_at to unicode_at for String

[Geequlim]

Close #15519

[akien-mga]

You changed the tab to spaces.

[Geequlim]

sorry clang-formate doesn't work for me on Windows. I will fix it when I get home

[akien-mga]

clang-format doesn't apply to the XML, for those you need to preserve the formatting manually.

[akien-mga]

GDNative fails building it seems:

modules/gdnative/gdnative_api_struct.gen.cpp:706:2: error: 'godot_string_ord_at' was not declared in this scope
  godot_string_ord_at,
  ^

[akien-mga]

I don't think it's worth breaking the API this late in the release cycle, and we only accept fixes to critical issues now (+ some enhancements to recent features like mono, bullet, gdnative, autotile, etc.).

We can consider it for 3.1 / 3.0.x, but then it will have to be added in a way that does not break compatibility (though ord_at should be kept, albeit with a deprecation warning announcing when it will be removed and pointing to the new method).

[Geequlim]

@akien-mga Is there a way to flag a method is deprecated?

[akien-mga]

Not yet, but there will be when we implement #4397.

[akien-mga]

Closing for now as we need a proper deprecation workflow before this can be implemented. I've listed it in #16863, so we can rediscuss it and maybe make the change later on.