Remove changes related to the unshipped threads everywhere feature, including commits b8da473da7 and 9f9e19e05d.
Since a version of Playbooks shipped calling this experimental API, keep a `nil` implementation to avoid breaking compatibility. We remove the hooks altogether, but keep the numbering again to avoid breaking compatbility.
Fixes: https://mattermost.atlassian.net/browse/MM-53358
It was a good decision in hindsight to keep the public module as 0.x
because this would have been a breaking change again.
https://mattermost.atlassian.net/browse/MM-53032
```release-note
Changed the Go module path from github.com/mattermost/mattermost-server/server/v8 to github.com/mattermost/mattermost/server/v8.
For the public facing module, it's path is also changed from github.com/mattermost/mattermost-server/server/public to github.com/mattermost/mattermost/server/public
```
We would return "nil, nil" if a plugin was on the blocklist.
This would cause a nil dereference panic while trying to add
struct fields from manifest to the audit logs.
To avoid it, we return an error explicitly and ignore the
error ids to unnecessarily have it log an error.
https://mattermost.atlassian.net/browse/MM-51786
```release-note
NONE
```
