Resolve Android security comments for Android ID migration.

- Use 32 byte key instead of 16 byte.
- Use HMAC-SHA256 instead of SHA256 for ssaid generation.
- Update HMAC with all package signatures.
- Use delimiter in between digest arguments.

This change will cause the ssaid of non-legacy installed apps (apps installed
post Android ID migration OTA) to change after an uninstall and reinstall sequence.

Bug: 34395671
Test: Unit tests, CTS tests, Manual tests
Change-Id: I19dec57947368ee5000c2c630b1e4030d46a4ab3