Add experimental tonemapper for Android 13

This has the following purposes:

1. Demonstrates the ability of libtonemap to swap out tonemapping curves
without invasive changes into dependent systems such as RenderEngine.
Notably, the only production code modified in this patch was
tonemap.cpp.
2. Assume a reasonable max content luminance. Some content may fail to
set a reasonable luminance level as part of their HDR10 metadata.
3. Track greylevels as piecewise linear interpolations, rather than
piecewise hermitians. This has the effect of smoothly converging to max
display luminance which can reduce banding effects in highights.

Bug: 200310159
Test: libtonemap_test
Test: HDR youtube
Change-Id: I08990aa402d6e503885e81397041f22957232079