Fix E2E test cases and setup for GHA (#26944)

* Fix E2E test cases and setup for GHA
* Fix more test cases, apply recommendations

e2e-tests/.ci/server.start.sh

@@ -19,4 +19,13 @@ if ! mme2e_wait_service_healthy server 60 10; then
   mme2e_log "Mattermost container not healthy, retry attempts exhausted. Giving up." >&2
   exit 1
 fi
+for MIGRATION in migration_advanced_permissions_phase_2; do
+  # Query explanation: if it doesn't find the migration in the table, there are 0 results and the command fails with a divide-by-zero error. Otherwise the command succeeds
+  MIGRATION_CHECK_COMMAND="${MME2E_DC_SERVER} exec -T -- postgres psql -U mmuser mattermost_test -c \"select 1 / (select count(*) from Systems where name = '${MIGRATION}' and value = 'true');\""
+  if ! mme2e_wait_command_success "$MIGRATION_CHECK_COMMAND >/dev/null 2>&1" "Waiting for migration to be completed: ${MIGRATION}" "30" "10"; then
+    mme2e_log "Migration ${MIGRATION} not completed, retry attempts exhausted. Giving up." >&2
+    exit 2
+  fi
+  mme2e_log "${MIGRATION}: completed."
+done
 mme2e_log "Mattermost container is running and healthy"