Speed up test database resets and Postgres config (#3238)

- Mount the test Postgres data directory on an in-memory tmpfs and disable fsync, synchronous_commit, and full_page_writes for ephemeral test containers.
- Override the Nomulus SQL dialect to emit 'deferrable initially deferred' on foreign keys exported by HibernateSchemaExporter. This matches prod.
- Replace per-test TRUNCATES (etc) with DELETEs -- the vast majority of
  tests only change a couple tables and DELETEing a few rows is much
faster than having to reallocate all the disk space for each and every
table every time
- Cache the connection to Postgres that we use for resetting data,
  instead of having to re-create it each time
- Add a test for child entity foreign key generation

This drastically speeds up tests, cutting out like 30-40% of total test
time (not including compilation)

(we also update a couple queries to be deterministically ordered to
avoid test flakes)

db/src/main/resources/sql/schema/db-schema.sql.generated

@@ -951,49 +951,49 @@
     alter table if exists "ConsoleUpdateHistory" 
        add constraint FKnhl1eolgix64u90xv3pj6xa3x 
        foreign key (acting_user) 
-       references "User";
+       references "User" deferrable initially deferred;
 
     alter table if exists "DelegationSignerData" 
        add constraint FKtr24j9v14ph2mfuw2gsmt12kq 
        foreign key (domain_repo_id) 
-       references "Domain";
+       references "Domain" deferrable initially deferred;
 
     alter table if exists "DomainDsDataHistory" 
        add constraint FKo4ilgyyfnvppbpuivus565i0j 
        foreign key (domain_repo_id, domain_history_revision_id) 
-       references "DomainHistory";
+       references "DomainHistory" deferrable initially deferred;
 
     alter table if exists "DomainHistoryHost" 
        add constraint FKa9woh3hu8gx5x0vly6bai327n 
        foreign key (domain_history_domain_repo_id, domain_history_history_revision_id) 
-       references "DomainHistory";
+       references "DomainHistory" deferrable initially deferred;
 
     alter table if exists "DomainHost" 
        add constraint FKeq1guccbre1yk3oosgp2io554 
        foreign key (domain_repo_id) 
-       references "Domain";
+       references "Domain" deferrable initially deferred;
 
     alter table if exists "DomainTransactionRecord" 
        add constraint FKcjqe54u72kha71vkibvxhjye7 
        foreign key (domain_repo_id, history_revision_id) 
-       references "DomainHistory";
+       references "DomainHistory" deferrable initially deferred;
 
     alter table if exists "GracePeriod" 
        add constraint FK2mys4hojm6ev2g9tmy5aq6m7g 
        foreign key (domain_repo_id) 
-       references "Domain";
+       references "Domain" deferrable initially deferred;
 
     alter table if exists "GracePeriodHistory" 
        add constraint FK7w3cx8d55q8bln80e716tr7b8 
        foreign key (domain_repo_id, domain_history_revision_id) 
-       references "DomainHistory";
+       references "DomainHistory" deferrable initially deferred;
 
     alter table if exists "RegistryLock" 
        add constraint FK2lhcwpxlnqijr96irylrh1707 
        foreign key (relock_revision_id) 
-       references "RegistryLock";
+       references "RegistryLock" deferrable initially deferred;
 
     alter table if exists "SignedMarkRevocationEntry" 
        add constraint FK5ivlhvs3121yx2li5tqh54u4 
        foreign key (revision_id) 
-       references "SignedMarkRevocationList";
+       references "SignedMarkRevocationList" deferrable initially deferred;

db/src/test/java/google/registry/sql/flyway/SchemaTest.java

@@ -18,6 +18,7 @@ import static com.google.common.truth.Truth.assertThat;
 import static google.registry.testing.truth.TextDiffSubject.assertThat;
 
 import com.google.common.base.Joiner;
+import com.google.common.collect.ImmutableMap;
 import com.google.common.flogger.FluentLogger;
 import com.google.common.io.Resources;
 import google.registry.persistence.NomulusPostgreSql;
@@ -81,7 +82,9 @@ class SchemaTest {
   private final PostgreSQLContainer<?> sqlContainer =
       new PostgreSQLContainer<>(NomulusPostgreSql.getDockerImageName())
           .withClasspathResourceMapping(
-              MOUNTED_RESOURCE_PATH, CONTAINER_MOUNT_POINT, BindMode.READ_WRITE);
+              MOUNTED_RESOURCE_PATH, CONTAINER_MOUNT_POINT, BindMode.READ_WRITE)
+          // Use tmpFs so that we keep everything in memory. No point in writing to disk
+          .withTmpFs(ImmutableMap.of("/var/lib/postgresql/data", "rw"));
 
   @Test
   @DisabledIfSystemProperty(named = "deploy_to_existing_db", matches = ".*")