composer: hold a sp<IComposer> from the service itself

IComposerClient assumes that IComposer will outlive its life cycle
and holds a simple pointer to HwcHal. This change is taking the same
approach of newer composer versions (2.2, 2.3, and 2.4) to make sure
that IComposer would outlive IComposerClient.

Test: coral booting with this change
Fixes: 155769496
Change-Id: I3962ede51ce823368c62c4e4e5fb30f7a5680bdf