### 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)

break;
			case TextServer::OVERRUN_TRIM_ELLIPSIS:
				overrun_flags.set_flag(TextServer::OVERRUN_TRIM);
				overrun_flags.set_flag(TextServer::OVERRUN_ADD_ELLIPSIS);
				break;
			case TextServer::OVERRUN_TRIM_WORD:
				overrun_flags.set_flag(TextServer::OVERRUN_TRIM);
				overrun_flags.set_flag(TextServer::OVERRUN_TRIM_WORD_ONLY);
				break;
			case TextServer::OVERRUN_TRIM_CHAR:
				overrun_flags.set_flag(TextServer::OVERRUN_TRIM);
				break;
			case TextServer::OVERRUN_NO_TRIMMING:
				break;
		}
		
		BitField<TextServer::JustificationFlag> line_jst_flags = jst_flags;
		if (!tab_stops.is_empty()) {
			line_jst_flags.set_flag(TextServer::JUSTIFICATION_AFTER_LAST_TAB);
		}
		if (autowrap_mode != TextServer::AUTOWRAP_OFF) {
			int visible_lines = get_visible_line_count();
			bool lines_hidden = visible_lines > 0 && visible_lines < lines_rid.size();
			if (lines_hidden) {
				overrun_flags.set_flag(TextServer::OVERRUN_ENFORCE_ELLIPSIS);
			}
			if (horizontal_alignment == HORIZONTAL_ALIGNMENT_FILL) {
				int jst_to_line = visible_lines;
				if (lines_rid.size() == 1 && line_jst_flags.has_flag(TextServer::JUSTIFICATION_DO_NOT_SKIP_SINGLE_LINE)) {
					jst_to_line = lines_rid.size();