Replace EnsureOpSpec and CleanOpSpec with ApplyOpSpec

[azriel91]

The ensure and clean operations are the same "apply" logic, with the target state either being the desired state, or the cleaned state.

Peace is intended to be able to support a set of target states such as "an empty set of servers", e.g. reusing servers for testing installation of software. This means arbitrary target states for each item -- "desired state for items a and b, but cleaned state for item c".

This may include some support to model "defined state" and "clean state" as top level concepts which are currently captured as separate commands.

• As part of this, move peace_core::progress to peace_cfg::resources.

[azriel91]

Tasks

• Rename EnsureOpSpec to ApplyOpSpec.

  fd -Ftf 'ensure_op_spec' -x bash -c 'mv $0 ${0/ensure_op_spec/apply_op_spec}' {}
  sd -s 'ensure_op_spec' 'apply_op_spec' $(fd -tf)
  sd -s 'EnsureOpSpec' 'ApplyOpSpec' $(fd -tf)
  sd -s 'Ensure OpSpec' 'ApplyOpSpec' $(fd -tf)
  sd -s 'ensure_op' 'apply_op' $(fd -tf)
  sd -s 'ensure op' 'apply op' $(fd -tf)
  sd '/// (.+) apply_op_spec(.*)' '/// $1 apply op spec $2' $(fd -tf)
  cargo fmt --all

• Add ItemSpec::state_clean to return an example of an empty State.

  On naming, because we want to consolidate functions into one trait (Consolidate Item Spec functions into single trait #96), we will likely have the following names:

  trait ItemSpec {
      async fn state_clean();
      async fn state_current();
      async fn state_desired();
  
      async fn try_state_current();
      async fn try_state_desired();
  }

• Split ApplyCmd from EnsureCmd, and take in target state, which may be state_desired or state_clean.

• EnsureCmd and CleanCmd both delegate to ApplyCmd.

• Update item specs to move CleanOpSpec logic into ApplyOpSpec.