Refactors`ui_text_remove_secondary_carets` from https://github.com/godotengine/godot/pull/68089 as `ui_text_clear_carets_and_selection`, with extra behaviour:
- If there's only one active caret active with a selection, clears the selection.
- In case there's more than one caret active, removes the secondary carets and clears selections.
With this change, `TextEdit` then imitates the behaviour of VSCode for clearing carets and selections.
Adds the bind `ui_text_remove_secondary_carets` to TextEdit, with ESC as the default shortcut.
When the bind is performed, if the TextEdit has multiple carets, `remove_secondary_carets` is called and secondary carets are removed.
This is useful when multiple selects are performed with `add_select_for_next_occurrence` #67644 or when multiple multiple carets are manually added, then it's possible to go back to a single caret with a shortcut.
Closes#67991
Adds the bind `add_selection_for_next_occurrence` to TextEdit, with CTRL+D as the default shortcut.
When the bind is performed, ff a selection is currently active with the last caret in text fields, searches for the next occurrence of the selection, adds a caret and selects the next occurrence.
If no selection is currently active with the last caret in text fields, selects the word currently under the caret.
The action can be performed sequentially for all occurrences of the selection of the last caret and for all existing carets. The viewport is adjusted to the latest newly added caret.
The bind and the behaviour is similar to VS Code's "Add Selection to Next Find Match" and JetBrains' "Add Selection for Next Occurrence". It takes advantage of the multi-caret API.
The default shortcut for `select_word_under_caret` has been changed to ALT+G, in order to give priority to CTRL+D for `add_selection_for_next_occurrence` to better align with popular IDEs and editors.
1. Viewport::get_visible_rect().position is always zero.
So Control::get_window_rect is identical to Control::get_global_rect.
Remove Control::get_window_rect since it is not used in the source code.
2. sqrt(a * a) = abs(a) for doubles
3. Simplify affine_inverse combination
4. Simplify calculation in shaders
The visibility of the `ScrollBar` was used as a condition for judging whether it should scroll.
**Visible** and **scrollable** are currently not the same in some cases (`SCROLL_MODE_SHOW_NEVER`).
This makes `SCROLL_MODE_SHOW_NEVER` not working properly.
This patch will make `SCROLL_MODE_SHOW_NEVER` available, so that the external `SrollBar` can
share the internal `ScrollBar`'s data, we can achieve the purpose of replacing the internal
`ScrollBar` with a custom external one.
