DO NOT MERGE: Update keystore and verity metadata signers

Use the same PKCS8 format as every other signing tool, and update
the signature format to use SHA-256 instead of SHA-1.

Bug: 15984840
Bug: 18120110
Change-Id: I6ac9e3594b5ae572f5b6763f3bd5b1bdb6ba2ad2
(cherry picked from commit 19c6bb5fe97c877976ef79762c6051223b8d2213)
2 files changed