feat: Add new method ValueContext.getBinder() with access to the current binder

[archiecobbs]

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Description

This implements feature request #19060 - Add new method ValueContext.getBinder() with access to the current binder.

Please see that issue for a discussion.

This PR is based on the initial prototype written by @mstahv.

This API change is completely backward-compatible with existing code.

Fixes #19060

Type of change

• [ ] Bugfix
• [X] Feature

Checklist

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

No explicit acceptance criteria were created however the unit test verifies that the feature is functioning as intended.

[github-actions[bot]]

Test Results

1 099 files  ± 0  1 099 suites  ±0   1h 21m 32s :stopwatch: -17s 7 010 tests + 1  6 961 :white_check_mark: + 1  49 :zzz: ±0  0 :x: ±0  7 355 runs   - 23  7 294 :white_check_mark:  - 23  61 :zzz: ±0  0 :x: ±0 

Results for commit be36b024. ± Comparison against base commit 3f74e8b0.

:recycle: This comment has been updated with latest results.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[tepi]

Related: https://github.com/vaadin/flow/issues/19211

[tepi]

Did a couple of fixes and a new PR here: https://github.com/vaadin/flow/pull/19487. Closing this one now.