fix: do not validate when focus is moving inside the field

[vursen]

Description

This PR prevents date-time-picker from being validated when focus is moving inside it, for example, between child pickers. The field should be only validated when focus moves away.

Fixes #4461

Type of change

• Bugfix

Checklist

• I have read the contribution guide: https://vaadin.com/docs-beta/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.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[vaadin-bot]

Hi @vursen , this commit cannot be picked to 23.1 by this bot, can you take a look and pick it manually?
Error Message: Error: Command failed: git cherry-pick baf313b
error: could not apply baf313b... fix: do not validate when moving focus inside the field (#4478)
hint: After resolving the conflicts, mark them with
hint: "git add/rm ", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".