### 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)

} else {
					if (line_jst_flags.has_flag(TextServer::JUSTIFICATION_SKIP_LAST_LINE)) {
						jst_to_line = visible_lines - 1;
					}
					if (line_jst_flags.has_flag(TextServer::JUSTIFICATION_SKIP_LAST_LINE_WITH_VISIBLE_CHARS)) {
						for (int i = visible_lines - 1; i >= 0; i--) {
							if (TS->shaped_text_has_visible_chars(lines_rid[i])) {
								jst_to_line = i;
								break;
							}
						}
					}
				}
				for (int i = 0; i < lines_rid.size(); i++) {
					if (i < jst_to_line) {
						TS->shaped_text_fit_to_width(lines_rid[i], width, line_jst_flags);
					} else if (i == (visible_lines - 1)) {
						TS->shaped_text_overrun_trim_to_width(lines_rid[i], width, overrun_flags);
					}
				}
			} else if (lines_hidden) {
				TS->shaped_text_overrun_trim_to_width(lines_rid[visible_lines - 1], width, overrun_flags);
			}
		} else {
			
			int jst_to_line = lines_rid.size();
			if (lines_rid.size() == 1 && line_jst_flags.has_flag(TextServer::JUSTIFICATION_DO_NOT_SKIP_SINGLE_LINE)) {
				jst_to_line = lines_rid.size();
			} else {
				if (line_jst_flags.has_flag(TextServer::JUSTIFICATION_SKIP_LAST_LINE)) {