feat: fire a validated event on validation and add shouldSetInvalid method

[mukherjeesudebi]

Description

1.Fires a validated event when the web component's validation takes place. 2.Adds a protected shouldSetInvalid() method. It will be used for preventing the web component from modifying the client-side invalid state on the Flow side afterward."

Fixes # (issue)

Type of change

• [ ] 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.

[CLAassistant]

All committers have signed the CLA.