Customize: Prevent using default template for a base control when it has...

Customize: Prevent using default template for a base control when it has content rendered on the server.

Also prevent invalid `type` attribute from being added to a `select` element.

See #30738.
Fixes #42286.

Built from https://develop.svn.wordpress.org/trunk@41952


git-svn-id: https://core.svn.wordpress.org/trunk@41786 1a063a9b-81f0-0310-95a4-ce76da25c4cd