feat: add partialSliced to support partial sliced attributes

[LucasXu0]

Add the partialSliced value to indicate whether the key should be sliced if the index is out of the attribute's range.

For example, if you only need to slice the attributes when the index is within the attribute's range, add the key to partialSliced.

**Hello World** <- If you input here, it should not follow the previous format if the partialSliced value contains the AppFlowyRichTextKeys.bold

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.

Project coverage is 72.15%. Comparing base (954ffa5) to head (c6e6da7).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/src/core/document/text_delta.dart	50.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #989      +/-   ##
==========================================
- Coverage   72.15%   72.15%   -0.01%     
==========================================
  Files         319      319              
  Lines       15221    15224       +3     
==========================================
+ Hits        10983    10985       +2     
- Misses       4238     4239       +1     

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