"default" attribute value for action and runner parameters is not validated against parameter schema during content register time

Let's say we have an action metadata definition file which looks like this:

parameters:
  cmds:
    description: Array of commands.
    #immutable: true
    type: array
    default: "foo"
...

During the register content phase, default value of that parameter won't be validated against the actual parameter type and schema and register step will succeed without any errors.

This value will only get validated during run time and that's when an error will be thrown if user tries to run that action.

For better end user experience and to go along with important "fail early and fast" mantra, we should also validate default attribute value for simple values (aka non-Jinja expressions which can only be validated during run time) and fail during content register time if this attribute fails the validation.

Start by locating the content registration validation path for action and runner parameter schemas, then trace how default values are handled. Make simple, non-Jinja defaults undergo schema validation during registration while leaving runtime-only expressions deferred; verify that the array example is rejected at registration time and valid defaults still register successfully.