Allow weekly email report to be sent daily

### Problem Statement

Currently, the [weekly report](https://docs.sentry.io/product/alerts/notifications/#weekly-reports) is limited to a weekly cadence.

The request is for an option to send this report daily.

There is a closed Github issue where [a comment that requested this had 9 thumbs](https://github.com/getsentry/sentry/issues/647#issuecomment-446737658) but was never addressed.

### Solution Brainstorm

Maybe, in addition to a weekly and daily option, Sentry could allow users to select a frequency for this report?

┆Issue is synchronized with this [Jira Improvement](https://getsentry.atlassian.net/browse/FEEDBACK-1713) by [Unito](https://www.unito.io)