Refactor names of internal scrollcapture interfaces

Renames to better align with use and existing naming patterns.
Using 'connection' to avoid confusion as to control flow or
roles. (A connection is direct from SystemUI --> App process)

IScrollCaptureClient -> IScrollCaptureConnection
IScrollCaptureController -> IScrollCaptureCallbacks

Test: atest FrameworksCoreTests:ScrollCaptureConnectionTest \
          FrameworksCoreTests:ScrollCaptureTargetResolverTest \
          ScrollCaptureTest

Change-Id: I9afd33109f6718b61d172ce3e4b3bb5d71a2897e