MM-44088: Add teamID filter to channelMembers (#20176)

We add 2 new params to channel members query.
1. Filter by teamId.
2. Negate that filter.

We include some more optimizations like:
- Moved the team role checks inside the dataloader.
- Moved the channel pretty name computation inside the loader.

Now that we load less data on initial load, we can reduce
the concurrency requirement to be a bit on the safer side.

```release-note
NONE
```

api4/schema.graphqls

@@ -19,6 +19,8 @@ type Query {
 		since: Float!): [String!]!
 	channelMembers(userId: String!,
 		channelId: String = "",
+		teamId: String = "",
+		excludeTeam: Boolean = false,
 		first: Int = 60,
 		after: String = "",
 		lastUpdateAt: Float = 0): [ChannelMember]!