[CTL] Fix RTL scrolling and tabs selection.

[bruvzg]

• Fixes RTL scrolling / content height calculation. Fixes RichTextBox cut down last lines scrolling (affects docs) #44484
• Fixes selection of tabs (and other space characters) with fonts that do not have glyphs for these characters. Fixes Tabs in TextEdit do not get highlighted when selected #44450
• Fixes non-integer text position with some scrollable controls.

[akien-mga]

I got that style issue too, it seems clang-format 11 changed its logic and produces a different result than 10 (used on CI): https://github.com/godotengine/godot/pull/44487/checks?check_run_id=1575457339

For now I've went with the git commit --no-verify approach to bypass pre-commit hooks and keep the clang-format 10 formatting, but eventually we should bump the version used on CI and have all contributors upgrade.

[bruvzg]

it seems clang-format 11 changed its logic and produces a different result than 10

Probably, I have clang-format 11 used in the git hook, and had similar styling issues with mismatching clang-format version in the past.

[akien-mga]

Thanks!