test: fix Session tests execution in random order

[gr8man]

Description
Ref: #9968

This PR fixes an issue that caused tests in the Session component to randomly fail with database errors (e.g., SQLite3Exception: table 'db_type_test' already exists) when executed with --order-by=random.

The root cause was traced to AbstractHandlerTestCase::setUp(), where parent::setUp() was being invoked before evaluating if the test should be skipped due to unsupported database drivers. Since parent::setUp() runs DatabaseTestTrait's migrations and initializes the test database (SQLite by default), skipping the test right after it meant that tearDown() was never executed by PHPUnit. As a result, the database was left dirty with leftover tables, which randomly broke subsequent database tests.

Moving markTestSkipped() above parent::setUp() cleanly skips the unsupported tests without initializing the database, ensuring 100% stability when running the suite in random order.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide