refactor(core): 💡 simpler names for declare APIs

[M-Adoo]

Purpose of this Pull Request

Simplify the names of the declare-related APIs

• Declare::declare_builder to Declare::declarer,
• DeclareBuilder to ObjDeclarer,
• DeclareBuilder::build_declare to ObjDeclarer::finish

Checklist Before Merging

Please ensure the following are completed before merging:

• If this is linked to an issue, include the link in your description.
• If you've made changes to the code or documentation, make sure these are updated in the CHANGELOG.md file.
• If you've introduced any break changes, briefly describe them in the Breaking section of the CHANGELOG.md file.

Additional Information

If you're unsure about which branch to submit your Pull Request to, or when it will be released after being merged, please refer to our Release Guide.

If you're working on a widget and need help writing test cases, we have some macros that can assist you. Please refer to the Ribir Dev Helper documentation.

[codecov]

Codecov Report

Attention: Patch coverage is 69.76744% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 85.48%. Comparing base (7d88e2c) to head (6981fe1).

Files	Patch %	Lines
core/src/builtin_widgets/anchor.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/cursor.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/delay_drop.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/fitted_box.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/focus_node.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/global_anchor.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/has_focus.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/layout_box.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/mouse_hover.rs	0.00%	1 Missing ⚠️
core/src/builtin_widgets/opacity.rs	0.00%	1 Missing ⚠️
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #547      +/-   ##
==========================================
- Coverage   85.50%   85.48%   -0.02%     
==========================================
  Files         180      180              
  Lines       26207    26207              
==========================================
- Hits        22408    22404       -4     
- Misses       3799     3803       +4     

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