Issue #3628599: Do not return the group and tag filters when loading entities

Leaves group and tag out of the return list in CiviEntityStorage::doLoadMultiple(). They are Contact.get filters; returning them joins the group, smart group cache and tag tables for every contact, and the groups and tags values are not used by any entity field.

They have been in the list since loads started returning every getfields key (2018). Of the 53 supported entities only Contact has them, and only in getfields for get.

The contact mock in CivicrmEntityTestBase now includes both in getfields, like the real API, so testLoadContact fails without the change.

Closes #3628599 (closed)

AI-Generated: Yes (Claude Code was used to help draft this change, its test and this description. I reviewed it.)