### Godot version

4.0.3 stable

### System information

Windows 10, i5 8600, RTX3060, 64 GB ram

### Issue description

In Godot 4, labels with lots of text cause scenes to load extremely slowly, both in the editor and in-game.

I measured a few game starts with different amounts of text in a label:

Text length | Game start time
-- | --
11323 | 2.33
22693 | 7.93
34064 | 19.69
45431 | 40.59

In Godot 3, the startup times for all test lengths was almost instantaneous.

The text I used was multiple copies of the license agreement for Google's [Roboto](https://fonts.google.com/specimen/Roboto) font. A "credits" page on a game could easily get well above this length.
Looking at a scatter plot with a best fit, it's pretty clearly increasing at around n^2:

![image](https://github.com/godotengine/godot/assets/8082633/6e2a9c41-f3fb-429d-acd3-288c24c6b744)

Results are the same whether I'm using the built-in font or a custom font, and results are similar across all renderers. Settings like text wrapping don't seem to affect it either.

### Steps to reproduce

Create a scene, add a label to that scene, and fill the label with a large amount of text. Try to launch the game and load that scene.

### Minimal reproduction project

[Godot3LargeLabel.zip](https://github.com/godotengine/godot/files/11521494/Godot3LargeLabel.zip)
[Godot4LargeLabel.zip](https://github.com/godotengine/godot/files/11521495/Godot4LargeLabel.zip)

}
		for (int i = 0; i < TextServer::SPACING_MAX; i++) {
			TS->shaped_text_set_spacing(text_rid, TextServer::SpacingType(i), font->get_spacing(TextServer::SpacingType(i)));
		}
		TS->shaped_text_set_bidi_override(text_rid, structured_text_parser(st_parser, st_args, txt));
		if (!tab_stops.is_empty()) {
			TS->shaped_text_tab_align(text_rid, tab_stops);
		}
		dirty = false;
		font_dirty = false;
		lines_dirty = true;
	}
	if (lines_dirty) {
		for (int i = 0; i < lines_rid.size(); i++) {
			TS->free_rid(lines_rid[i]);
		}
		lines_rid.clear();
		BitField<TextServer::LineBreakFlag> autowrap_flags = TextServer::BREAK_MANDATORY;
		switch (autowrap_mode) {
			case TextServer::AUTOWRAP_WORD_SMART:
				autowrap_flags = TextServer::BREAK_WORD_BOUND | TextServer::BREAK_ADAPTIVE | TextServer::BREAK_MANDATORY;
				break;
			case TextServer::AUTOWRAP_WORD:
				autowrap_flags = TextServer::BREAK_WORD_BOUND | TextServer::BREAK_MANDATORY;
				break;
			case TextServer::AUTOWRAP_ARBITRARY:
				autowrap_flags = TextServer::BREAK_GRAPHEME_BOUND | TextServer::BREAK_MANDATORY;
				break;
			case TextServer::AUTOWRAP_OFF:
				break;