### 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)

int line_spacing = settings.is_valid() ? settings->get_line_spacing() : theme_cache.line_spacing;
	Ref<StyleBox> style = theme_cache.normal_style;
	int lines_visible = lines_rid.size();
	if (max_lines_visible >= 0 && lines_visible > max_lines_visible) {
		lines_visible = max_lines_visible;
	}
	minsize.height = 0;
	int last_line = MIN(lines_rid.size(), lines_visible + lines_skipped);
	for (int64_t i = lines_skipped; i < last_line; i++) {
		minsize.height += TS->shaped_text_get_size(lines_rid[i]).y + line_spacing;
		if (minsize.height > (get_size().height - style->get_minimum_size().height + line_spacing)) {
			break;
		}
	}
	if (minsize.height > 0) {
		minsize.height -= line_spacing;
	}
}
inline void draw_glyph(const Glyph &p_gl, const RID &p_canvas, const Color &p_font_color, const Vector2 &p_ofs) {
	if (p_gl.font_rid != RID()) {
		TS->font_draw_glyph(p_gl.font_rid, p_canvas, p_gl.font_size, p_ofs + Vector2(p_gl.x_off, p_gl.y_off), p_gl.index, p_font_color);
	} else {
		TS->draw_hex_code_box(p_canvas, p_gl.font_size, p_ofs + Vector2(p_gl.x_off, p_gl.y_off), p_gl.index, p_font_color);
	}
}
inline void draw_glyph_outline(const Glyph &p_gl, const RID &p_canvas, const Color &p_font_color, const Color &p_font_shadow_color, const Color &p_font_outline_color, const int &p_shadow_outline_size, const int &p_outline_size, const Vector2 &p_ofs, const Vector2 &shadow_ofs) {