feat: enable signals to have fine-grained validations

[taefi]

Description

This adds the API for adding fine-grained validators for different signal operations.
Fixes #2835

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

All modified and coverable lines are covered by tests ✅

Project coverage is 92.64%. Comparing base (0a9bd31) to head (8abec4f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2888   +/-   ##
=======================================
  Coverage   92.64%   92.64%           
=======================================
  Files          83       83           
  Lines        2842     2842           
  Branches      739      739           
=======================================
  Hits         2633     2633           
  Misses        158      158           
  Partials       51       51           

Flag	Coverage Δ
unittests	92.64% <ø> (ø)

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[sonarcloud]

Quality Gate passed

Issues
0 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 SonarQube Cloud