Rust code changes:
  - add Rhai scripting as a feature (--features=rhaiscript)
  - add ArchiveInspector for access to RawHubrisArchive
  - add "system(argv) -> #{exit_code, stdout, stderr}" from std::process::Command
  - export faux-mgs paramsters to Rhai main.
  - run any faux-mgs command with "let result = faux_mgs(["arg0", .. "argN"]);
      - faux-mgs results are passed back to the script as a map even if they are simpler JSON.
  - ChronoPackage for time handling.
  - FilesystemPackage for file access.
  - EnvironmentPackage for env var access.
  - export "scriptdir" so that script can get other files relative to itself.
  - "verify_rot_image()" to verify a RoT image vs CFPA, CMPA.
  - vars available to main():
      - "argv" - script main's scope passing all remaining CLI args.
      - "rbi_default" - expose faux-mgs default "rot_boot_info" version
      - "interface" - pass the "--interface INTERFACE" value.
      - "reset_watchdog_timeout_ms" - pass that value to the script.
  - Route Rhai's debug function to the faux-mgs log.
      - The `debug("message")` function is routed to the faux-mgs slog logging.
        Prefixing a message with "crit|", "trace|", "error|", "warn|", "error|", or "debug|"
        will log at that corresponding level. Leaving off the prefix or using some other
        prefix will log at the debug level.
      - Rhai's `print()` still goes to stdout.

Rhai scripts:

scripts/util.rhai contains common script and faux-mgs support.
  - getops()
  - to_hexstring()
  - cstring_to_string(a)
  - array_to_mac(a)
  - ab_to_01(v)
  - env_expand(s, override)
  - rot_boot_info()
  - state()
  - caboose_value(component, slot, key)
  - get_device_cabooses()
  - rkth_to_key_name(rkth)
  - array_to_blob(a)
  - get_cmpa()
  - get_cfpa()
  - get_rot_keyset()

scripts/update-rollback.rhai
  - Only use MGS messages for testing, no humility or other APIs
  - perform happy path update and rollback from baseline to under-test images.

scripts/targets.json
  - an example configuration script for scripts/update-rollback.rhai

Fix `json_to_map()` so that JSON errors are reported properly.
Some calls to `print()` change to logging to debug or info.
Add configuration for `faux-ipcc`.
  - since system() needs to be used to run faux-ipcc, should there
    be a regex to parse or are Rhai's existing string functions
    sufficient to pull out certs and measurements? Since faux-ipcc
    doesn't handle attestations yet, we'll wait a bit.

Move RawHubrisArchive knowledge to a separate source file.

Also work around baseline not implementing transient boot preference

Also error handling in to_hexstring.

Positional baseline and UT args become options.
Remove dead code.
Add docs and tests for getopts

Power control is needed to test recovery from failed RoT updates when
using transient boot preference and fault insertion.

Checkin TEST_PLAN.md for upgrade-rollback tests
Update TODO.md for upgrade-rollback tests
The FMR script helps when running single commands from the repo that use rhai scripts.

  - Fix `faux_mgs` rhai function to return full error text.
  - Changed `util::set_rot_boot_preference()` to `util::rot_boot_preference(...,
    action, ...)`
  - Test recovery flows for dealing with previous failed or abandoned updates that
    set RoT image preferences.

Also: Update scripts test plan, scripts todo list, and remove Hubris issue #2093 workaround.