Tests for serde across std/no_std

[andrewdavidmackenzie]

See if we can add unit tests for the two different implementations of serde of structs between piggui/piglet and porky, to ensure binary format compatibility?

One idea would be an integration level test that goes through all the structs in hw_definition, and in a no_std test renders them to file, then another set of std tests ensures that can all be read and match the expected result.

Then do the opposite, render from std_tests to file and read from no_std program somehow?