cleanup "presubmit"->"preupload" references

This codebase was originally based on CrOS which used the term
"presubmit".  For AOSP, we renamed to "preupload" to better reflect
when these checks were run.  But it seems like we missed some spots,
so clean up the remaining references.  Most were internal anyways.

Bug: None
Test: unittests pass
Change-Id: I91454a61551574110054afe6a715d484eac2f483