Add sdr white point information to composer3

* Add layer-level SDR white point. When there are mixed HDR/SDR layers
on the display, HDR layers should remain at display brightness, or
whatever the HDR standard is (e.g., keep HLG content at 1000 nits), while
SDR layers should be "dimmed" to the appropriate perceptual brightness.
* Add SDR white point to the client composited client target buffer.
When there are mixed HDR/SDR layers in client compostion, HWC must tell
SurfaceFlinger the target white point of the client target buffer so
that SurfaceFlinger-applied dimming may be atomically applied as a
brightness mode change.

Bug: 200310158
Test: builds

Change-Id: Ifbfe3125ede1a4de04978c6e644a5c911c33d3b6