[React][Next.js] DateField empty value is not treated as empty

[illiakovalenko]

• This PR follows the Contribution Guide
• Changelog updated
• Upgrade guide entry added

Description / Motivation

The default DateField value provided by Layout Service is date, we need to rely on it and on empty string value as well

Testing Details

• Unit Test Added
• Manual Test/Other (Please elaborate)

Types of changes

• Bug fix (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 change)

[yavorsk]

Looks good!
As discussed: there is a potential issue if we have a text field and its value is equal to the default empty date value - then the field will be treated as empty. We decided to not cover this edge case, since the scenario is not valid in general.