This is a rollup of recent work. Changes include:
- Creating an xpcshell only updater binary. This binary has an embedded xpcshell only cert for verifying test only mars. It is only used by tests and is not signed w/ authenticode certs.
- Modifying tests to use that new binary
- Adding a check-cert option to the maintenance service
- Using that new cert-check option in new tests to test the authenticode path
- No longer doing an authenticode check during service updater tests on the xpcshell binary.
- Enables more tests for other platforms
