appropriate error messages added for date and datetime picker

[PallaviGanorkar]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Fixes #1589

Description

1. Displaying appropriate error messages for date picker for format validation and required=true/false
2. Displaying appropriate error messages for date time picker for format validation and required=true/false

Alternative(s) considered yes , BY By implementing date formatter, which validates answer is set then its valid format because in UI after successful parsing of date in required format its set to Questionnaire answer

Type Choose one: Bug fix

Screenshots (if applicable) : Video is attached for all 4 scenarios

date_picker_required_false.webm date_picker_required_true.webm date_time_picker_required_false.webm date_time_picker_required_true.webm

Checklist

• [x] I have read and acknowledged the Code of conduct.
• [x] I have read the Contributing page.
• [x] I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA.
• [x] I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• [x] I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project.
• [x] I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally.
• [x] I have built and run the demo app(s) to verify my change fixes the issue and/or does not break the demo app(s).