fix: implement toString, equals, hashCode for Key implementation used…

[denis-anisimov]

… in "of"

fixes #8474 and #4626

Description

Please list all relevant dependencies in this section and provide summary of the change, motivation and context.

Fixes # (issue)

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.

[vaadin-bot]

SonarQube analysis reported 1 issue

1. Key.java#L2729: Reduce this anonymous class number of lines from 32 to at most 20, or make it a named class.

[vaadin-bot]

Hi @denis-anisimov and @caalador, when i performed cherry-pick to this commit to 2.7, i have encountered the following issue. Can you take a look and pick it manually?
Error Message:
Error: Command failed: git cherry-pick b6cf0b5
error: could not apply b6cf0b5... fix: implement toString, equals, hashCode for Key implementation used in "of" (#11837)
hint: after resolving the conflicts, mark the corrected paths
hint: with 'git add ' or 'git rm '
hint: and commit the result with 'git commit'