COOLDOWN/SWITCH_GROUP/DRY_RUN actions don't work with QUERY_LIMIT

[JmPotato]

Bug Report

1. Minimal reproduce step (Required)

CREATE RESOURCE GROUP IF NOT EXISTS rg1 RU_PER_SEC = 5000 QUERY_LIMIT=(RU=1, ACTION=COOLDOWN);

2. What did you expect to see? (Required)

The COOLDOWN action should be triggered, and the corresponding identity match record must be present in mysql.tidb_runaway_queries. SWITCH_GROUP and DRY_RUN also exhibit the same phenomenon.

3. What did you see instead (Required)

Nothing happened.

4. What is your TiDB version? (Required)

ced1490

[JmPotato]

We check RU and PROCESSED_KEYS only in CheckThresholds, however, it only supports KILL action now, which means that the COOLDOWN, SWITCH_GROUP and DRY_RUN actions won't work in this case.

tidb/pkg/resourcegroup/runaway/checker.go

Lines 323 to 325 in ced1490

	if r.settings == nil || r.settings.Action != rmpb.RunawayAction_Kill {
	return err
	}