Split local/absolute include into attributes

Previously these were expanded into copts, requiring making all includes
absolute and duplicating includes to account for potentially generated
files. We now can handle both of these properly on the Bazel side, so
let's clean up build files a bit.

Test: bp2build.sh
Change-Id: I6c6160738cd6c269408c6c7a37010654d84f3c9d