feat: add automatic unsubscription from the signal instance

[taefi]

Description

This also postpones subscribing to a signal
instance until the client-side signal is
actually being subscribed to (rendered).

Fixes #2621

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/guide/contributing/overview/
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.

Additional for Feature type of change

• Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.

[codecov]

Codecov Report

Attention: Patch coverage is 91.89189% with 3 lines in your changes missing coverage. Please review.

Project coverage is 92.15%. Comparing base (0ebdc3e) to head (ba6e41c).
Report is 4 commits behind head on main.

Files	Patch %	Lines
packages/ts/react-signals/src/EventChannel.ts	86.95%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2656      +/-   ##
==========================================
- Coverage   92.17%   92.15%   -0.02%     
==========================================
  Files          78       78              
  Lines        2454     2486      +32     
  Branches      634      639       +5     
==========================================
+ Hits         2262     2291      +29     
- Misses        145      148       +3     
  Partials       47       47              

Flag	Coverage Δ
unittests	92.15% <91.89%> (-0.02%)	⬇️

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[sonarcloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[taefi]

Closed due to the refactoring done in #2657, and in favor of #2663