Add firmware version-specific tests

[1Blademaster]

The ftp tests don't pass until 4.6.0, but all the others pass at 4.2.0. ( Tested all the minor versions so 4.x.0 )

I imagine there would be some differences in FTP that were introduced in 4.6.0. Will add "latest", "stable" and "4.6.3" version tests to the github tests workflow, maybe create a test matrix for this.

Originally posted by @1Blademaster in #1138 (comment)

[1Blademaster]

Hopefully we can cache builds for specific firmwares between workflow runs so it doesn't take ages to rebuild the sim.