Fix deadlock when calling dumpsys surfaceflinger

We were holding the state lock when calling into the main thread to
access some debug data. The main thread was stuck waiting for the
state lock, causing the deadlock.

Fix by cleaning up the surface flinger dumpsys and reduce the scope
of the state lock.

Fixes: 313910768, 300525768
Test: dumpsys SurfaceFlinger
Test: dumpsys SurfaceFlinger --hwclayers
Test: dumpsys SurfaceFlinger --frontend
Test: dumpsys SurfaceFlinger --timestats --proto
Change-Id: Id62b9427a14bc37bc92759fbaa8ca2b3da94905d