GraphQL: Unlock goroutine throttle to match batch capacity (#20146)

We were throttling the amount of concurrent resolvers
at a given time. The idea behind this was to avoid overloading
the database with too many requests.

However, with the introduction of dataloaders, this limitation
actually becomes a bottleneck because all DB calls are actually
batched, so we are unnecessarily throttling the amount of
items that can be processed in a single batch.

The only caveat with this is that now all resolvers
need to backed by dataloaders, or otherwise not be queried
as part of a loop.

In a subsequent PR, we will be removing channel stats
from under channel to be a top-level object to be returned
for a given channel.

```release-note
NONE
```

app/users/users.go

@@ -93,6 +93,10 @@ func (us *UserService) GetUser(userID string) (*model.User, error) {
 	return us.store.Get(context.Background(), userID)
 }
 
+func (us *UserService) GetUsers(userIDs []string) ([]*model.User, error) {
+	return us.store.GetMany(context.Background(), userIDs)
+}
+
 func (us *UserService) GetUserByUsername(username string) (*model.User, error) {
 	return us.store.GetByUsername(username)
 }
@@ -105,7 +109,7 @@ func (us *UserService) GetUserByAuth(authData *string, authService string) (*mod
 	return us.store.GetByAuth(authData, authService)
 }
 
-func (us *UserService) GetUsers(options *model.UserGetOptions) ([]*model.User, error) {
+func (us *UserService) GetUsersFromProfiles(options *model.UserGetOptions) ([]*model.User, error) {
 	return us.store.GetAllProfiles(options)
 }
 
@@ -114,7 +118,7 @@ func (us *UserService) GetUsersByUsernames(usernames []string, options *model.Us
 }
 
 func (us *UserService) GetUsersPage(options *model.UserGetOptions, asAdmin bool) ([]*model.User, error) {
-	users, err := us.GetUsers(options)
+	users, err := us.GetUsersFromProfiles(options)
 	if err != nil {
 		return nil, err
 	}