Added SQLite bigpk test. Moved schema builder patterns spreadsheet to docs/internals folder.

tests/framework/db/QueryBuilderTest.php

@@ -145,6 +145,7 @@ abstract class QueryBuilderTest extends DatabaseTestCase
                 [
                     'mysql' => 'bigint(20) NOT NULL AUTO_INCREMENT PRIMARY KEY',
                     'postgres' => 'bigserial NOT NULL PRIMARY KEY',
+                    'sqlite' => 'bigint PRIMARY KEY AUTOINCREMENT NOT NULL',
                 ],
             ],
             [