This used to be a part of MDL-44615 but I want to move it into separate issue because it is a very useful function and it looks like MDL-44615 is going to be delayed.

I add a function cm_info::get_course_module_record() that allows to get an object from cm_info that is exactly the same as record in course_modules.

Also it can be used instead of get_coursemodule_from_id() which is a very expensive function:

$cm = get_coursemodule_from_id(null, $cmid, $courseid, true, MUST_EXIST);

may be substituted with:

$cm = get_fast_modinfo($courseid)->get_cm($cmid)->get_course_module_record(true);

Assuming we are talking about current course, everything is already cached and the second option performs no DB queries.

unittest included