[META] Port all necessary tests to D6

Motivation
Since we've got a D6 version of Selenium, we need to check and re-implement if necessary all tests we need for D6. Also we should decide which of these tests are only D7-related.
Here is the list of tests:

• #1229274: Test for textarea.js
• #1229264: Test for states.js
• #1229266: Test for tabledrag.js
• #1229272: Test for tableselect.js
• #1229268: Test for tableheader.js
• #1229276: Test for vertical-tabs.js
• #1229258: Test for autocomplete.js
• #1229260: Test for collapse.js
• #1229262: Test for machine-name.js