Phase Behavior of Telechelic Polyisobutylene in Subcritical and Supercritical Fluids. 3. Three-Arm-Star PIB (4K) as a Model Trimer for Monohydroxy and Dihydroxy PIB (1K) in Ethane, Propane, Dimethyl Ether, Carbon Dioxide, and Chlorodifluoromethane