"Find" and "Find Next" should highlight found text, so any typing/pasting replaces found text

[ArdaE]

Godot version:
Godot 3.0 through 3.1 Alpha 3.

OS/device including version:
macOS 10.13.6

Issue description:
A common feature of all IDE editors I've ever used is that typing text after a Find operation replaces the found text. In Godot's text editors (GDScript and shader editors), a box is drawn around each occurrence of the searched text and the cursor moves to the next box with each Find Next operation, but the text that the cursor moves next to is not actually selected. This results in a very unusual (as far as text editors go) behaviour where typed/pasted text is appended to the found text instead of replacing it, even though the found text looks like it was selected due to the box around it and hence should have gotten replaced.

So my request is to please automatically select the current occurrence of the searched text that the cursor is placed next to as a result of a "Find" or "Find Next" operation.

P.S. #2982 seems to track script editor related enhancement requests, which might be a good place to add this.