tests: Construct two bad packages at runtime for VerifierTest.

For the BadPackage tests from VerifierTest: one alters the footer, and
the other alters the metadata. Move the two tests to be based on
otasigned_v3.zip (they're based on otasigned_v1.zip previously). Also
construct the testdata files dynamically (to save the space and for
better readability).

Test: recovery_component_test
Change-Id: I7604d563f8b4fa0c55fec8730c063384158e3abc