Add PostgreSQL version of SQLite integ tests

- Add PostgreSQL throwaway database
- Add optional length parameter for random string
- Fix syntax for PostgreSQL in several areas
- Add optional ID for whereById type determination

tests/integration/sqlite/FindTest.php

@@ -82,8 +82,6 @@ class FindTest extends TestCase
     {
         $docs = Find::byFields(ThrowawayDb::TABLE, [Field::GT('num_value', 100)], TestDocument::class);
         $this->assertNotNull($docs, 'There should have been a document list returned');
-        $count = 0;
-        foreach ($docs->items() as $ignored) $count++;
         $this->assertFalse($docs->hasItems(), 'There should have been no documents in the list');
     }