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.


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git-svn-id: http://core.svn.wordpress.org/trunk@28452 1a063a9b-81f0-0310-95a4-ce76da25c4cd