Fix CodeEdit hover word lookup

[kitbdev]

• Fixes Hovering while holding control over a path with spaces doesn't always recognize the path #102431

Fixes hovering to show tooltip when over the end of the last character of a symbol (where clicking would place the caret at the end).
This should be useful for cases like godotengine/godot-proposals#11365 and #102380, since selecting the entire word puts the caret at the last character.

Unifies the word detection behavior to the one that the rest of the TextEdit uses.
This fixes hovering to show tooltip not working correctly when next to unicode word break characters. Custom word separators are now respected too.
Removed the old word detection function.

Moves the string detection logic to use CodeEdit's delimiter system. Though this means it won't work in comments anymore.

Also made the tooltip hover work when text is selected. There shouldn't be any problem with allowing this, since the tooltip doesn't show if mouse buttons are held. Related: godotengine/godot-proposals#12492

[Ivorforce]

Core wise, moving a domain specific function out of core is always welcome :)

[Repiteo]

Thanks!