The PR enhances DatePickerI18n with methods for setting error messages and updates the DatePicker's validation logic to show these error messages when validation fails.
[!WARNING]
The PR is marked as breaking because it causes the component to start overriding any custom error messages that were set manually with the setErrorMessage method before validation. If you need to set error messages manually, use setManualValidation(true), which prevents the component from updating the invalid and errorMessage properties, allowing you to control them manually.
Description
The PR enhances DatePickerI18n with methods for setting error messages and updates the DatePicker's validation logic to show these error messages when validation fails.
Part of #4618
Type of change