Change Display White Balance to track the Planckian locus

Currently when DWB adjusts the display's white point it uses standard
Illuminant D to convert CCT to CIE xy coordinates. This causes a slight
green tint, detectable by some users. Change this behavior to calculate
CIE xy based on the Planckian locus.

Bug: 128712066
Test:
a. Manual, by overriding target DWB CCT and observing resulting target
xy coordinates
b. atest FrameworksServicesTests:ColorDisplayServiceTest, making sure
there are no new failures (existing failures tracked in a separate bug)

Change-Id: I6fa336ee694730df45d5eacceb442aa556b5718e