Provide ability to specify jobs defined in checks configuration as objects

[weierophinney]

Feature Request

Q	A
New Feature	yes
BC Break	no

Summary

Currently, the "checks" element is expected to be an object with the following schema:

{
  "name": "(string) Name of the check being run",
  "operatingSystem": "(string) Name of the OS the job should be run on (generally ubuntu-latest)",
  "action": "(string) GHA to run the step on; currently ignored",
  "job": "(string) JSON object detailing the job"
}

For configuration purposes, it would be easier if the "job" element of a check could be an actual JSON object:

{
  "name": "...",
  "operatingSystem": "..."
  "action": "..."
  "job": {
    "php": "php version",
    "extensions": [],
    "ini": [],
    "dependencies": "...",
    "command": "..."
  }
}

Each of "extensions", "ini", and "dependencies" are technically optional, but SHOULD be provided; I'd suggest we raise a notice of some sort in the action if they are missing.

For BC purposes, we should allow either a JSON string OR an object.