registration: Add resource template-like functionality to extension.json

registration: Add resource template-like functionality to extension.json

This allows for extensions to specify common arguments to ResourceLoader
module definitions by only specifying them once.

The only supported values are "localBasePath" (which is relative to the
current directory), "remoteSkinPath", and "remoteExtPath". If a module
is using a custom class or is already specifying paths, the default paths
will not be added.

Tests are included to cover existing functionality and newly added
functionality. The convertExtensionToRegistration.php script was also
extended to try and guess what the default paths should be.

Bug: T88786
Change-Id: I802461796e8d8584dacf3b0c811b5ba97a4a8f7f