We were incorrectly not broadcasting status cache updates
inspite of that being an LRU cache.
We were also not doing it for profilesInChannel cache.
Now we fix it by properly checking the invalidationEvent
which is something local to the cache itself rather
than the cache provider.
https://mattermost.atlassian.net/browse/MM-62077
```release-note
NONE
```
We were using a mock cache provider which mixed up LRU caches
with each other. This led to incorrect unmarshalling method calls.
We fix this by using the real cache provider.
https://mattermost.atlassian.net/browse/MM-60413
```release-note
NONE
```
If the store fails to initialize (e.g. run a migration), it would `log.Fatal` and then `os.Exit`. Unfortunately, this trips up `TestMain`, which happily keeps running tests, now guaranteed to fail.
Avoid this by instead returning an error from the store initialization, handling appropriately at the layer above.
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
```
