Move signing related options to a shared place

Move OTA signing flags to payload_signer.py so that we can re-use these
flags in multiple binaries.

Test: th
Bug: 293313353
Change-Id: I44f9910cee37c449397e174a5784f747ec9fb0d6

tools/releasetools/ota_utils.py

@@ -37,7 +37,6 @@ OPTIONS.force_non_ab = False
 OPTIONS.wipe_user_data = False
 OPTIONS.downgrade = False
 OPTIONS.key_passwords = {}
-OPTIONS.package_key = None
 OPTIONS.incremental_source = None
 OPTIONS.retrofit_dynamic_partitions = False
 OPTIONS.output_metadata_path = None