Jetpack Backup: Add Calendar / Search to Enter Date

#### Is your feature request related to a problem? Please describe.

Going to Jetpack > Backup shows the latest date when backup was made. Although it's possible to select previous days using `<` arrow, it could take a while to go to a much previous date.

A workaround would be to set the date (example August 9, 2021) `20210809` from the URL: `https://wordpress.com/backup/testsitename.wpcomstaging.com?date=20210809`.

#### Describe the solution you'd like

A calendar to pick backup date, or search box to enter date.

#### Additional context

Start in the Jetpack > Backup view and inspect how the URL's date parameter selects a backup date. Define the calendar or date-entry interaction, then verify that choosing a much earlier date loads the corresponding backup instead of requiring repeated arrow clicks.

Written by the indexing model from the issue text.