[FEATURE] sap.ui.core.testfwk: Add HCB to possible themes in m lib

Change-Id: Ic51d04d862c086a9892580fd8aab6effe71e1082
Signed-off-by: Evgeni Katsarski <evgeni.katsarski@sap.com>
Merge "[FEATURE] sap.ui.core.testfwk: Add HCB to possible themes in m lib"