feat: improved session serialization debug tool

[mcollovati]

Description

The tool now works only with --add-opens and extendedDebugInfo system property. Unserializable objects are replaced by null and restored during deserialization to avoid NPEs. Object with throwing toString are replaced with an object capable to serialize fields and regenerate the original object type on deserialization.

Fixes #45

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.
• [ ] 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.

[mcollovati]

This draft PR is a placeholder for session serialization debug tool improvements. Code needs to be cleaned and simplified.