MDL-34397 TEMP FIX FOR MDL-40830
MDL-34397 Reset cache in API functions instead of tests

- moveto_module() already resets the cache, no need to call reset in the tests
- groups_add_member() and groups_remove_member() must reset cache and tests must not
MDL-34397 Move course content cache to MUC
MDL-34397 small improvements to get_fast_modinfo()
MDL-34397 removing references to course.modinfo
MDL-40843