Cherry picked fixes to URL datatype (v6.2.x)

[SDScandrettKint]

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Description of Change

Fixes to URL datatype cherry picked from the 7.5.x PR #10642 including preventing the URL label from being saved without URL, URL label able to be added if the URL has already been saved and allowing the inputted (but not saved) data to persist if navigated to a different card.

Issues Solved

#8451, #10027 and #10592

Checklist

• Unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Ticket Background

• Sponsored by: Knowledge Integration
• Found by: @SDScandrettKint
• Tested by: @SDScandrettKint
• Designed by: @SDScandrettKint

Further comments

[chiatt]

Closing because the fix to the url datatype should accompany a migration to url tile data. #10642 (comment)
The severity of this bug doesn't warrant a data migration in a patch version.