Revert "Ensure user_email is automatically tagged (tests)"

This reverts commit 24e9d229e009561195f4600651c6f483bd675d91.
Revert "Always tag user email addresses"

This reverts commit f9fb2be73c5eff1417d991b258a69bbed1ec7fde.

(This maintains the users_seen column)
Change how user identifiers are stored (and dont rip out sentry_user_emails, but deprecate it).