Remove resource groups

[mosabua]

As discussed in the Trino Gateway dev sync there is a mismatch in the location of the code for resource groups (in Trino), the use (mostly in Trino and NOT in Trino Gateway) and the UI for editing (in Trino Gateway).

Given this situation, we plan to remove the UI code from Trino Gateway and ideally someone can port the UI over to Trino, specifically the preview UI in Trino since that has similar tooling.

Here are some more details from @willmostly :

• Resource Groups are not used by the Trino Gateway, so they cannot be properly tested
• Managing a Trino component through the Gateway introduces coupling that can cause issues such as Datastore migrations mismatch with the Trino cluster resource manager db #637
• Our current test framework has no capability for testing Trino Gateway against different Trino versions, so we will be unaware of any compatibility issues
• The existing implementation can create an incorrect impression that Trino Gateway uses resource groups for load balancing and routing, which it does not

Considering these factors, the convenience of the resource group UI does not justify the maintenance overhead and potential for issues.

If we want to have something akin to resource groups for different cluster in Trino Gateway is a separate topic. The answer to that is probably yes in the long run .. but it would NOT be based on the resource groups in Trino itself.