perf(repository): add indexes on sp_action.rollout and rollout_group

Rollout monitoring queries (existsByRolloutId, getStatusCountByRolloutId,
getStatusCountByRolloutGroupId) filter by rollout or rollout_group on
sp_action. The flyway baseline did not index either column, so Postgres
falls back to Seq Scan on every monitoring poll. With 16k action rows
this is meaningful — the group-count query takes ~500 ms without the
index and ~27 ms with it (Index Only Scan, Heap Fetches: 0).

Bench (16k rows, 1000 iter):
- WHERE tenant=? AND rollout_group=?           18.6x faster on PG
                                               17.6x faster on YugabyteDB
- WHERE tenant=? AND rollout=? GROUP BY status  2.5x faster on PG
                                                1.5x faster on YugabyteDB

Adds V1_20_2 sibling migrations for POSTGRESQL, H2, and MYSQL.

Author: clayly

hawkbit-repository/hawkbit-repository-jpa-flyway/src/main/resources/db/migration/H2/V1_20_2__action_rollout_indexes__H2.sql

@@ -0,0 +1,3 @@
+-- See POSTGRESQL/V1_20_2__action_rollout_indexes__POSTGRESQL.sql for rationale.
+CREATE INDEX sp_idx_action_rollout_status ON sp_action (tenant, rollout, status);
+CREATE INDEX sp_idx_action_rollout_group  ON sp_action (tenant, rollout_group);

hawkbit-repository/hawkbit-repository-jpa-flyway/src/main/resources/db/migration/MYSQL/V1_20_2__action_rollout_indexes__MYSQL.sql

@@ -0,0 +1,3 @@
+-- See POSTGRESQL/V1_20_2__action_rollout_indexes__POSTGRESQL.sql for rationale.
+CREATE INDEX sp_idx_action_rollout_status ON sp_action (tenant, rollout, status);
+CREATE INDEX sp_idx_action_rollout_group  ON sp_action (tenant, rollout_group);

hawkbit-repository/hawkbit-repository-jpa-flyway/src/main/resources/db/migration/POSTGRESQL/V1_20_2__action_rollout_indexes__POSTGRESQL.sql

@@ -0,0 +1,9 @@
+-- Add indexes covering rollout-monitoring queries on sp_action.
+--
+-- existsByRolloutId, getStatusCountByRolloutId, getStatusCountByRolloutGroupId
+-- (and similar JPA queries) filter by rollout / rollout_group; the baseline did
+-- not index either column, so Postgres falls back to Seq Scan over sp_action on
+-- every monitoring poll. With 16k action rows the group-count query takes ~500 ms
+-- without the index and ~27 ms with it (Index Only Scan, Heap Fetches: 0).
+CREATE INDEX sp_idx_action_rollout_status ON sp_action (tenant, rollout, status);
+CREATE INDEX sp_idx_action_rollout_group  ON sp_action (tenant, rollout_group);