feat: log all exceptions caught by RetryRule

[mcollovati]

Description

Currently, RetryRule show details only of the last caught exception, but this one may not be the real reason of the test failure. This change prints the stack trace of all caught expections when debug level for RetryRule is at least 'debug', helping the develper to detect the real cause of the test failure.

Fixes #1527

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.