Move cagg_invalidation to solo tests

The cagg_invalidation test stops the background workers and performs
tests with invalidations. However, they the test was running in a
parallel group, and background workers could be activated by other
tests, leading to flaky test behavior. This PR moves the
cagg_invalidation tests to the solo tests.

tsl/test/sql/CMakeLists.txt

@@ -121,6 +121,7 @@ set(SOLO_TESTS
     cagg_bgw
     cagg_ddl-${PG_VERSION_MAJOR}
     cagg_dump
+    cagg_invalidation
     move
     reorder
     telemetry_stats-${PG_VERSION_MAJOR})