DatePicker: Required field asterisk bug fix

[lynamemi]

Pull request checklist

• Addresses an existing issue: Fixes DatePicker - Extra required indicator (*) #4278
• Include a change request file using $ npm run change

Description of changes

DatePicker was rendering two extra icons for required fields: One after the label, one after the input field, and one under the input if no error message is specified:

• Using TextField's label because TextField already has the support to add an icon only after the label, if there is one, or only after the input field, if there is no label.
• Removing the asterisks that replace error message. Need to have the blank space in the string to pick up the error message styling on the input field.
• Added a new 'required' example to show these two variants.
• Added example styling that matches the TextField example page (improves legibility with width and spacing).

After:

Focus areas to test

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