F Prime supported mode management

[timcanham]

Many flight systems use modes to enable or disable commands. F Prime currently requires ad-hoc solutions to implement mode management and commanding. A component is required to add project-specific ports and components to check modes. There is a Roses issue to discuss this pattern:

#3302

This discussion is to add mode as a first-class concept in F Prime.

FPP

The supported modes could be represented by an FPP enumeration stored in the project configuration:

    enum SpaceCraftMode {
      @ Some initialization mode
      SC_MODE_IDLE
      @ Safe Mode
      SC_MODE_SAFE
      @ Tracking a UFO mode
      SC_MODE_TRACKING 
    }

This FPP type would be specifically for mode management, and would be customized for each project.

There would be a new port in /Fw/Mode/Mode.fpp:

  port Mode(
               mode: SpaceCraftMode @< Spacecraft mode
             )

Components would specify commands in FPP with a new command tag:

@ No-op command
    async command CMD_TEST_CMD_1(
                                  arg1: I32 @< The I32 command argument
                                  arg2: F32 @< The F32 command argument
                                  arg3: U8 @< The U8 command argument
                                ) \
      opcode 2 \
      mode SC_MODE_SAFE

(Still working on it, don't comment yet...)