[WIP] Presort text draw calls.

[bruvzg]

Pre-sort text draw calls to improve batching, should significantly reduce draw call number for languages with a lot of glyphs and multiline text with outlines/shadow.

TODO:

• TextEdit
• Test and adjust RTL nested frame draw order.
• Cleanup duplicate code.
• Document new methods.

Before:

After:

Fixes #107109
Fixes #104537

[bruvzg]

Some extra tests:

1. Label with CJK test using system font fallback.

4.5 beta 3 - FPS: 330, draw calls 967
this PR - FPS: 1980, draw calls 14

2. Label with Latin text.

4.5 beta 3 - FPS: 1570, draw calls 50
this PR - FPS: 1740, draw calls 2
(as expected, much lower difference)

3. RTL with CJK text:

4.5 beta 3 - FPS: 315, draw calls 980
this PR - FPS: 2080, draw calls 15

4. BBCode demo:

4.5 beta 3 - FPS: 145, draw calls 45
this PR - FPS: 145, draw calls 23
(FPS seems to be linited by constant redraws of the RTL, not number draw calls)

5. 500 random Labels with outline.

4.5 beta 3 - FPS: 380, draw calls 1000
this PR - FPS: 380, draw calls 1000
(can't be batched, labels are different canvas items and have specific draw order)