[3.x] Fix RichTextLabel auto-wrapping on CJK texts

[timothyqiu]

This PR fixes #21482.

There is still 1 px difference between when they wrap the last character after this fix. This is becauses Label autowraps if the text chunk width >= frame width, while RichTextLabel autowraps if text chunk width > frame width. I think this is not related to the original issue and worth a dedicated PR if desired.

Complex Text Layout on the master branch is the proper way to solve the wrapping problem, but it seems that it won't be backported.

This PR also supersedes #45290. I also added a fix to solve the issue mentioned in #45290 (comment), allowing word breaking on CJK and non-CJK edge. I'll revert this additional fix if it should be a separate PR.

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Before: (there is unexpected linebreak after "Hopefully, ", and "should" wraps after "sh")

After:

[timothyqiu]

@bruvzg I used a slightly different range than you suggested.

• Ends CJK Unified Ideographs at 9FFF instead of 9FCB, the latter is the end of assigned code points as of Unicode 5.2, but expanded to the end of the block in later versions.
• Added F900 - FAFF, the CJK Compatibility Ideographs block
• Added 30000 - 3134F, the CJK Unified Ideographs Extension G block
• Added FF65 - FF9F and FFA0 - FFDC for halfwidth form of katakana and compatibility jamo

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.3.3.