Sign MicrdroidTestApp using APK sig scheme V4

... and copy the idsig file to the device.

Note that the copied idsig file is not used currently, because
mk_payload can't handle the file yet.

Bug: N/A
Test: atest MicrodroidHostTestCases
Change-Id: I7db582ac7933decfe00395ebe83e146ed61618a6
4 files changed