Fix: Fixed issue where renaming a tag wouldn't save the new name

[ferrariofilippo]

Resolved / Related Issues

• Were these changes approved in an issue or discussion with the project maintainers? In order to prevent extra work, feature requests and changes to the codebase must be approved before the pull request will be reviewed. This prevents extra work for the contributors and maintainers.
  Closes Bug: Renaming a tag doesn't save the changes #12535
  Related Tags reset everytime you restart app #14362

Notes
When editing a tag, we need to instantiate a new TagViewModel so that CachingJsonSettingsDatabase.SetValue() -> UpdateValueInCache() will find a difference between the old and the new list, hence saving the changes.
Before we were making a shallow-copy of the tag, causing changes to affect the object in both the lists

Validation
How did you test these changes?

• Did you build the app and test your changes?
• Did you check for accessibility? You can use Accessibility Insights for this.
• Did you remove any strings from the en-us resource file?
  • Did you search the solution to see if the string is still being used?
• Did you implement any design changes to an existing feature?
  • Was this change approved?
• Are there any other steps that were used to validate these changes?
  1. Rename/Change the color of two or more tags
  2. Save Changes
  3. Restart the app
  4. Check that changes were applied

[yaira2]

LGTM