Toyota: Add SECOC longitudinal control

[chrispypatt]

• Add counter for secoc acc messages like the other secoc messages
• Add new acc message creation for second ACCEL_CMD
• Remove SECOC openpilotLongitudinalControl disable

This will be accompanied by this related panda safety PR: commaai/panda#2061

[jyoung8607]

Long term I'd like to clean up the SecOC message wrapping convention, but that's a separate refactor that we don't need to get into for this PR.

For development purposes we've gotten away with setting the accel value in both ACC control messages, but before we merge we need to match stock actuation behavior: always set zero/inactive acceleration in ACC_CONTROL, and only send the true accel in ACC_CONTROL_2. There are checks in commaai/panda#2072 to ensure this correct behavior.

Aside from that, LGTM.

[nelsonjchen]

Just passing a Discord Link here to some of the chatter on the state of the PR:

Nov 21: "Well the mutation tests are failing so something seems wrong functionally. But I would also say my attempt at supporting two acc commands in the tests is a bit gross"

https://discord.com/channels/469524606043160576/905950538816978974/1309380353261174847