Add cashing for groups by member method

### Description

Based on https://github.com/keycloak/keycloak/pull/45956#discussion_r2758538588 there has been removed the cashing for `getOrganizationGroupsByMember`. There is now new usage which requires to add the cache back: https://github.com/keycloak/keycloak/pull/46062/changes#diff-512eb46b43f07e04467c4dc4c839161c355fe18679cadc8a336c528d68510e54R107