Improve system modules tests

The previous approach of looking for substrings in the command that
matched the base name of the jar could not differentiate between
whether the jar was a prebuilt or a source as they both have the same
base name.

The tests also did not cover the case when there was both prebuilts
and source modules.

This change:
1. Checks that the inputs to the command come from the appropriate
   module.
2. Adds a mixed test.
3. Deduped the source and prebuilt module definitions.

The new test reveals the buggy behavior which will be fixed in a follow
up change.

Bug: 182402568
Test: m nothing
Change-Id: I384ecca097cbe3560e7589c23fb99c176a42fd9b