Cleanup for `switch` statements:
* Move `default` to the bottom in `WP_Theme_Install_List_Table`
* `switch/endswitch` syntax is not supported in Hack. Switch to `switch (...) {  .... }` syntax. (A few template-type instances linger).

Fixes #28409.
See #27881.



git-svn-id: https://develop.svn.wordpress.org/trunk@28633 602fd350-edb4-49c9-b593-d223f7449a82