test: run the unit suite on MariaDB only, and on the panel's own stack

The suite ran on in-memory SQLite, an engine production never uses: it hid
column lengths, MySQL-only syntax and type coercion (the identity bug fixed in
the previous commit passed CI that way). SQLite is gone:

- TestDb connects only to MariaDB/MySQL (XCVM_TEST_DB_DSN/_USER/_PASS; root over
  the local socket, else 127.0.0.1:3306). Each instance gets a throwaway
  schema, dropped with it, in the installer's sql_mode, with an explicit
  connect timeout (a boot under test can zero default_socket_timeout).
- InstallSchema and the tests take the production DDL as is: the SQLite
  reducers, the keys they re-added, the faked information_schema and the
  sqliteCreateFunction() stand-ins are removed; test DDL is MySQL DDL.
- ReplicaBootTest, DbConnectRefusalTest and LazyDatabaseHandlerTest reach the
  test server instead of SQLite files; RecordingFinalizer no longer swallows
  an information_schema failure "for tests on SQLite".
- `make test-db` starts a throwaway mariadb:11.4 (tmpfs) for a machine without
  a server; the CI PHPUnit job gets the same as a service.

The suite also runs on a panel host with the bundled PHP and its own php.ini:
tests reach the code through MAIN_HOME, not `<repo>/src`; repository checks
and process-isolated tests (ionCube Loader + OPcache CLI segfault on a script
read from stdin) are in the skip-on-panel group; xcvm_test_child_php() starts
a child that fakes \XC_VM without the real extension; Redis-down tests use
RedisManager::useConnector() instead of an eval'd \XC_VM.

Stale opt-in tests fixed on the way: the real-agent provisioning test answers
the agent-started check, the extension integration test sends the typed starts
and reads the binary signature raw, a fake producer starts as PHP_BINARY, and
the certbot test waits for the line its background command writes.

tests/Unit/DaemonLoopTest.php

@@ -21,7 +21,7 @@ final class DaemonLoopTest extends TestCase {
 	public function testNoDaemonLoopEndsWithAnUnconditionalBreak(): void {
 		$rChecked = 0;
 
-		foreach (glob(dirname(__DIR__, 2) . '/src/Cli/Commands/*Command.php') ?: [] as $rFile) {
+		foreach (glob(MAIN_HOME . 'Cli/Commands/*Command.php') ?: [] as $rFile) {
 			$rLines = file($rFile) ?: [];
 			if (!str_contains(implode('', $rLines), 'restartDaemon(')) {
 				continue;