Assert that PIXEL_FORMAT_R_8 == AIDL version

I4846327b29736ee811672801a683deb287342a8e added PIXEL_FORMAT_R_8 to
match the AIDL version, but due to tricky dependencies, it hardcoded the
constant, rather than referring to it directly. Add a static assert in
a new file verifying that they match.

Bug: 154720547
Bug: 209497983
Bug: 193170859
Test: make
Change-Id: I43fd2bc53eba8c9decc64fc9563c625f56c71798