resourceloader: Simplify load.mock.php by removing includes dependency

resourceloader: Simplify load.mock.php by removing includes dependency

It previously depended on Xml.php for Xml::encodeJsCall, which
in turn depends on FormatJson. Other Xml.php methods also depend
on Sanitizer, but that was carefully not triggered.

Avoid both of these by simply constructing the string inline,
and using json_encode() directly for the one variable parameter.

Also, fix the names of one of the ResourceLoaderTest cases for
dotless module names. It claims to have been added to cover a
regression fixed in r88706, but that commit seems rather unrelated.
A bit of searching revealed as the relevant commit instead.

Bug: T188076
Change-Id: I04851d0355227f3a6b79b8d41a51d4beadce0e80