SF: Dump CompositionEngine layers and cleanup output

No code was calling compositionengine::Layer::dump. This adds a call,
and cleans up a few odd details about the output so it looks
reasonable.

Test: dumpsys SurfaceFlinger
Bug: 121291683

Change-Id: Iad524ddcd1fe99c0a1670a8ebb045ecbffd5b2eb