### Godot version

8449592d92eaeef990f5502b419d491ee3eeb7a6

### System information

Windows 11

### Issue description

Zooming in the script editor on an empty script freezes the entire editor for a few seconds, but if the file is large then it freezes for 4-5 seconds (which is unacceptable). Looks like a recent regression.

### Steps to reproduce

Just zoom in/out on the large script file.

### Minimal reproduction project

N/A
PackedByteArray imgdata_b;
	imgdata_b.resize(w * h * 2);
	uint8_t *wb = imgdata_b.ptrw();
	PackedByteArray imgdata_a;
	imgdata_a.resize(w * h * 2);
	uint8_t *wa = imgdata_a.ptrw();
	for (int i = 0; i < h; i++) {
		for (int j = 0; j < w; j++) {
			int ofs_src = (i * w + j) * 4;
			int ofs_dst = (i * w + j) * 2;
			wr[ofs_dst + 0] = 255;
			wr[ofs_dst + 1] = r[ofs_src + 0];
			wg[ofs_dst + 0] = 255;
			wg[ofs_dst + 1] = r[ofs_src + 1];
			wb[ofs_dst + 0] = 255;
			wb[ofs_dst + 1] = r[ofs_src + 2];
			wa[ofs_dst + 0] = 255;
			wa[ofs_dst + 1] = r[ofs_src + 3];
		}
	}
	Ref<Image> img_r = memnew(Image(w, h, 0, Image::FORMAT_LA8, imgdata_r));
	set_texture_image(0, Vector2i(p_sz, 0), p_page * 4 + 0, img_r);
	Ref<Image> img_g = memnew(Image(w, h, 0, Image::FORMAT_LA8, imgdata_g));
	set_texture_image(0, Vector2i(p_sz, 0), p_page * 4 + 1, img_g);
	Ref<Image> img_b = memnew(Image(w, h, 0, Image::FORMAT_LA8, imgdata_b));
	set_texture_image(0, Vector2i(p_sz, 0), p_page * 4 + 2, img_b);
	Ref<Image> img_a = memnew(Image(w, h, 0, Image::FORMAT_LA8, imgdata_a));
	set_texture_image(0, Vector2i(p_sz, 0), p_page * 4 + 3, img_a);
}
void FontFile::_convert_packed_4bit(Ref<Image> &p_source, int p_page, int p_sz) {