LPS-49135 Each PortalCache needs a bootstrap loader, set null for all implementations for now, will replace it with specific bootstrap loader later.
LPS-49135 Fix unit tests.
LPS-49135 Move deferred cache loading logic from EhcacheStreamBootstrapCacheLoader to StreamBootstrapHelpUtil
LPS-49135 Rename class, no changes.
LPS-49135 Rename attributes and inner class.