Require APK Signature Scheme v2 for ephemeral APKs

This makes Package Manager require APK Signature Scheme v2 signatures
for ephemeral APKs. This part of the effort to deprecate the v1
signature scheme based on JAR signing.

Test: cts-tradefed run singleCommand cts --skip-device-info --skip-preconditions --skip-connectivity-check --abi arm64-v8a --module CtsAppSecurityHostTestCases -t android.appsecurity.cts.PkgInstallSignatureVerificationTest
Bug: 33700225
Change-Id: I3b408487c07085c0a7924d3eca495bdcb344b32d