Add a test for tx messages

[markopetkovic96]

#32425
I made a PR to get more information about this test. As I asked, after checked rx example, should the tx messages be similar to the rx messages? Create a packet, transmit can messages (with safety_tx_hook), update openpilot, and compare it with the previous panda state?

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[sshane]

The goal of the issue isn't to copy the existing test changing rx for tx. We want to ensure that any control message openpilot generates (CAN) the panda will accept and not block, causing a potential controls mismatch. The trick is getting openpilot to generate varied, but valid, messages to test with.