Removes the `bind_email` and `bind_msisdn` parameters from the `/register` C/S API endpoint as per [MSC2140: Terms of Service for ISes and IMs](https://github.com/matrix-org/matrix-doc/pull/2140/files#diff-c03a26de5ac40fb532de19cb7fc2aaf7R107).

Very small code cleanup.

Previously the stats were not being correctly populated.

* Ensure the list media admin API is always available

This API is required for some external media repo implementations to operate (mostly for doing quarantine operations on a room).

* changelog

Adjust su-exec to only be used if needed.

If UID == getuid() and GID == getgid() then we do not need to su-exec, and chmod will not work.

* Ensure an auth instance is available to ListMediaInRoom

Fixes https://github.com/matrix-org/synapse/issues/5737

* Changelog

Remove all the "double return" statements which were a result of us removing all the instances of

```
defer.returnValue(...)
return
```

statements when we switched to python3 fully.

Trace device list changes.

These methods were part of the v1 C/S API. Remove them as they are no longer used by any code paths.

* fix thumbnail storage location

Signed-off-by: Lorenz Steinert <lorenz@steinerts.de>

* Add changelog file.

Signed-off-by: Lorenz Steinert <lorenz@steinerts.de>

* Update Changelog

Signed-off-by: Lorenz Steinert <lorenz@steinerts.de>

Signed-off-by: Aaron Raimist <aaron@raim.ist>

This reverts commit 4765f0cf.

Python will return a tuple whether there are parentheses around the returned values or not.

I'm just sick of my editor complaining about this all over the place :)

Adds a flag to `/versions`' `unstable_features` section indicating that this Synapse understands what an `id_access_token` is, as per https://github.com/matrix-org/synapse/issues/5927#issuecomment-523566043

Fixes #5927

This reverts commit 71fc0406.

This broke 3PID invites as #5892 was required for it to work correctly.

Exempt support users from consent