Reworked the USWDS date picker and restored original features for controlling the min/max dates in the date picker in the time span controls

Before making a pull request

• Put the appropriate EXEMPT flag if needed in the MR title (see https://practices.wma.chs.usgs.gov/practice/peer_code_review/)
• Run all linters (make lint)
• Run all tests (make test)
• Update the changelog appropriately
• If making a release, update code.json, versionNumber and metadataLastUpdated.

Description

Updated the USWDSDatePicker to include initializing the USWDS date picker within the component. In order to do this, the code must wait until after loading is complete before adding the 'usa-date-picker' class to the markup. Then added a "changeDate" event to the picker that is emitted when the date picker is used to change the date.

Updated time span controls to fully reimplement the features to set the min/max/range dates when the startDate and endDate are updated. Added code to handle clearing the pickers when the selectedTimeSpan changes to a ISO duration.

After making a pull request

• If appropriate, put the link to the PR in the JIRA ticket
• Assign someone to review unless the change is trivial