* MM-45956: Optimize FileInfo stats query
We Denormalize Post.ChannelId on FileInfo.ChannelId
```release-note
The file info stats query is now optimized by denormalizing the channelID column into the table itself. This will speed up the query to get the file count for a channel on clicking the RHS.
Migration times:
On a MySQL 8.0.31 DB with
1405 rows in FileInfo and 11M posts, it took around 0.3s
On a Postgres 12.14 DB with
1731 rows in FileInfo and 11M posts, it took around 0.27s
```
https://mattermost.atlassian.net/browse/MM-45956
