Use sha256 of a string as seed in RapporEncoder.insecureEncoder

Test: atest android.privacy.LongitudinalReportingEncoderTest
Test: atest android.privacy.RapporEncoderTest
Test: atest android.server.net.watchlist.PrivacyUtilsTests

Bug: 76001602
Change-Id: I42d569f34d29125e7adf898b9553053a42149bd4
5 files changed