Refactor FW action go code

[LeanSheng]

Make FW action code to be more modular.

• Fix current action code:

  • coreboot.go: break it into packages #57

• Add support for:

  • build FSP #64 (later changed to refactor edk2 builds #92)
  • build edk2payload #65
    • also edk2 full package and edk2 driver (might need edk2 platform)
    • full package / payload / driver should differ only by provided config)
    • Update: they differ also by building command, should be solved in issue refactor edk2 builds #92
  • add support for building u-root initramfs #242
  • build linuxboot payload
  • build OpenBMC Automatically test built Docker containers for open-BMC #25
  • build EC FW (zephyr) Automatically test built Docker containers for Zephyr #26
  • build u-BMC Automatically test built Docker containers for u-BMC #24

[AtomicFS]

Once #61 gets merged, can task build linuxboot payload be considered as complete? Or are there some other acceptance criteria? @LeanSheng