Improve printing of Display- and Layer- Settings

In order to add any shaders to our cache warming code, we need to look
at the logcat to see what settings created a particular shader. Update
the PrintTo methods to be simpler and provide more information.

Add fields that were missing from operator==, and add operator!= where
necessary.

Add tests for the missing fields.

LayerSettings:
- If a matrix is Identity, simply print "I". This cuts down on a lot of
  noise. Do the same for DisplaySettings.
- Similarly, if the ShadowSettings or StretchEffect is the default, skip
  it.
- PixelSource: only print the Buffer OR the SolidColor; only one is
  respected anyway.
- Reorder printing to line up with the order of declaration.
- Remove 'Defining PrintTo helps with Google Tests.' This method is more
  generally useful.

SkiaGLRenderEngine:
- Set kFlushAfterEveryLayer to kPrintLayerSettings. These are
  compile-time constants, and they're typically modified together.
- The LayerSettings include several lines of text. Instead of splitting
  them up at an arbitrary boundary, splitting words, break them up based
  on the newline character. This makes the logs much easier to read.
- Move this into a common function so that we can also print the
  DisplaySettings, which may impact what shaders are compiled.

Bug: 190487656
Bug: 222355787
Test: perfetto
Test: LayerSettingsTest and DisplaySettingsTest
Change-Id: Ifc464779ed368d2edad7fc6adab53e9b368fd7cb