Add "delete all data" option when removing CC

[timbocode]

Is your feature request related to a problem? Please describe. Currently WC and CC do not delete data / database tables when they are uninstalled. This can leave a lot of useless data clogging up the database.

Describe the solution you'd like An option button that gives the user the choice of whether or not they want the data to be removed, set to "no" by default. An option to export the data (in a format that can be reimported) before removing it would also be useful.

Describe alternatives you've considered It's possible to remove the data manually from the database but this should not be necessary and would be beyond the means of most end users.

Additional context WC and CC both give a scary warning that data will be deleted but this doesn't happen. This warning is misleading.

See also https://github.com/ClassicPress-research/classic-commerce/issues/136#issuecomment-562888969