Migrate common processor code to internal

[wagoodman]

This is in preparation for grype DB schema 6 in #2125. This PR migrates some of the common utility functions to an internal package.

[kzantow]

tests is a common name for a variable holding a set of table tests, as it looks like you noticed and renamed due to lint/shadowing rules -- I might opt to keep this named something like testutil, not blocking, though.

[wagoodman]

@kzantow agreed, adjusted to make them all testUtils