Add APK container signing key/cert pairs for APEXes

Created via
openssl req -x509 -newkey rsa:4096 -nodes -days 999999 -keyout key.pem -out com.android.tzdata.x509.pem
openssl pkcs8 -topk8 -inform PEM -outform DER -in key.pem -out com.android.tzdata.pk8 -nocrypt

Test: m com.android.tzdata
jarsigner -verify -verbose -certs out/target/product/blueline/system/apex/com.android.tzdata.apex shows
...
X.509, CN=com.android.tzdata, OU=Android, O=Android, L=Mountain View, ST=California, C=US

Change-Id: I19f6efaaa6468e65e9891e4e61704fb48f0b986a