Add hide events filter in admin timeline

[RichardTaylor]

This could be part of admin/timeline or it could be a separate admin page.

The purpose would be internal transparency / oversight / governance.

The prominence reasons for messages / and classifications for whole threads could be shown, perhaps with options to hide certain types of case eg. spam.

An internal transparency log of sorts.

[garethrees]

Timeline seems the most suitable place (#1748), since that's just rendering a subset of events as it is. When adding the new set of events we'd probably want to add a new filter option.

[RichardTaylor]

Linking to the ticket for the public version of this #2657

[HelenWDTK]

This issue has been automatically closed due to a lack of discussion or resolution for over 12 months.
Should we decide to revisit this issue in the future, it can be reopened.