Remove the concept of target dataspace

This is only needed for configuring colorspace agnostic dataspaces, but
no device does that. For colorspace agnostic layers, it's sufficient to
just use the colormode dataspace, with the possible exception of HDR
where we can preserve some bespoke logic, so we can just get rid of
target dataspaces and any associated plumbing.

Bug: 292162273
Test: builds
Test: libsurfaceflinger_unittest
Test: libcompositionengine_test
Change-Id: I319bb354e80e3ad1eaaacd896b897e6696f96588