Add backend validation for Adhoc testing

[philemone]

Describe your changes

Right now adhoc testing only validates types of expression, not validators. This MR adds new endpoint for adhoc testing to move all parameters validation to backend.
It addition this MR adds change to string formatter to remove single quotes while no value is stored inside string field.

Checklist before merge

• Related issue ID is placed at the beginning of PR title in [brackets] (can be GH issue or Nu Jira issue)
• Code is cleaned from temporary changes and commented out lines
• Parts of the code that are not easy to understand are documented in the code
• Changes are covered by automated tests
• Showcase in dev-application.conf added to demonstrate the feature
• Documentation added or updated
• Added entry in Changelog.md describing the change from the perspective of a public distribution user
• Added MigrationGuide.md entry in the appropriate subcategory if introducing a breaking change
• Verify that PR will be squashed during merge

[github-actions]

created: #6993
⚠️ Be careful! Snapshot changes are not necessarily the cause of the error. Check the logs.

[Dzuming]

LGTM