feat: support formatting text when the composing range is not collapsed

[LucasXu0]

Before that, we only supported formatting text when the selection was collapsed and the composing range was collapsed.

For some IMEs, especially those combining backtick with other characters to input a new character, the composing range is not collapsed before formatting text.

Solution: Check if the newly input character is formattable, even if the composing range is not collapsed. If so, format it; otherwise, ignore it.

showcase.mp4

[codecov]

Codecov Report

Attention: Patch coverage is 36.73469% with 31 lines in your changes missing coverage. Please review.

Project coverage is 72.17%. Comparing base (737681d) to head (9697064).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...rvice/ime/delta_input_on_non_text_update_impl.dart	14.28%	18 Missing ⚠️
...component/service/ime/non_delta_input_service.dart	0.00%	8 Missing ⚠️
lib/src/core/location/selection.dart	0.00%	4 Missing ⚠️
...rmat_single_character/format_single_character.dart	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #900      +/-   ##
==========================================
- Coverage   72.30%   72.17%   -0.13%     
==========================================
  Files         317      317              
  Lines       14822    14866      +44     
==========================================
+ Hits        10717    10730      +13     
- Misses       4105     4136      +31     

Flag	Coverage Δ
	72.17% <36.73%> (-0.13%)	⬇️

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