Rename hwc-specific methods and properties for readability

In hint session timing code, "present" is used to refer to:

1) The CompositionEngine present method called in SF
2) The present method in Output called separately per-display
3) The present call made to the actual vendor HWC
4) The place where the frame actually starts to display on the screen
   eg: expectedPresentTime

The distinctions is important in a timing context because they behave
differently and happen at different points in the frame, but they are
currently referred to interchangeably. This patch aims to remove some
of that ambiguity by prefixing hwc-specific methods + properties with
"hwc" as well as making fence naming more specific.

Bug: b/195990840
Test: atest libsurfaceflinger_unittest:libsurfaceflinger_unittest.AidlPowerHalWrapperTest
Change-Id: I138e197431a5f1af05031e1180483433009c333d