Fix phone home stats

Add some exception handling here so that events whose json cannot be parsed are
ignored rather than getting us stuck in a loop.

Fixes #6404.

Only do `rc_login` ratelimiting on succesful login.

Co-Authored-By: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Co-Authored-By: Brendan Abolivier <babolivier@matrix.org>

Signed-off-by: James Hebden <james@ec0.io>

* 'develop' of github.com:matrix-org/synapse:
  Blacklist PurgeRoomTestCase (#6361)
  Set room version default to 5

Set room version default to 5

Fix the SQL SELECT query in _paginate_room_events_txn

Split purge API into events vs state and add PurgeEventsStorage

MSC2326: Add background update to take previous events into account

... and update INSTALL.md to include py3.8.

We'll also have to update the buildkite pipeline to run it

Co-Authored-By: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

Co-Authored-By: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

This reverts commit 1186612d.

Doing a SELECT DISTINCT when paginating is quite expensive, because it requires the engine to do sorting on the entire events table. However, we only need to run it if we're filtering on 2+ labels, so this PR is changing the request so that DISTINCT is only used then.