fix(core): emit tuiDropdownOpenChange on distinct values

[shiv9604]

Fixes #9609

Description :

1. We used Subject because we are concerned about the latest value compared to maintaining the last state.
2. Created the emitOpenChange method to centralize & handle responsibility for emitting values.
3. Replaced previous value emission logic with the currently integrated flow.

[lumberjack-bot]

Pull request was closed ✔️

All saved screenshots (for current PR) were deleted 🗑️

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 66.17%. Comparing base (b94bec5) to head (c07231c).
Report is 17 commits behind head on main.

Files with missing lines	Patch %	Lines
...ectives/dropdown/dropdown-open-legacy.directive.ts	20.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9962      +/-   ##
==========================================
- Coverage   75.26%   66.17%   -9.09%     
==========================================
  Files        1249     1214      -35     
  Lines       19607    15702    -3905     
  Branches     2033     2307     +274     
==========================================
- Hits        14757    10391    -4366     
- Misses       4806     5073     +267     
- Partials       44      238     +194     

Flag	Coverage Δ
summary	66.17% <33.33%> (-9.09%)	⬇️

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[bundlemon]

BundleMon

Files updated (1)

Status	Path	Size	Limits
✅	demo/browser/main.(hash).js	304.11KB (+31B +0.01%)	+10%

Unchanged files (4)

Status	Path	Size	Limits
✅	demo/browser/vendor.(hash).js	260.19KB	+10%
✅	demo/browser/runtime.(hash).js	43.93KB	+10%
✅	demo/browser/styles.(hash).css	19.63KB	+10%
✅	demo/browser/polyfills.(hash).js	11.18KB	+10%

Total files change +31B 0%

Groups updated (1)

Status	Path	Size	Limits
✅	demo/browser/*..js	7.38MB (+31B 0%)	-

Final result: ✅

View report in BundleMon website ➡️

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