Use static build rules in snapshot generation

It is easier to extract information out of static build rules than it
is out of custom build rules built using the builder as the former
provides access to the in/out and args separate from the rule whereas
the latter only provides access to in/out.

Also, cleans up some warnings that appear in Intellij.

There is a lot of duplication in the testing code. That will be
resolved in a follow up change.

Bug: 143678475
Test: m conscrypt-module-sdk
Change-Id: I973bc0c90b0affd84487f1b222dd3e6c22c07ec0