Support .actor folder as source to build actor and test

[ruocco-l]

As of now the library hinges on a very rigid folder structure: actors/OWNER_ACTOR-NAME/. or standalone-actors/OWNER_ACTOR-NAME/. This means that basic actor, like the ones from templates cannot be tested with this tool.

Solving this will mean to find a reliable way to find the correct id (owner/actor-name) of the actor, knowing only the actor name from actor.json.

Possible ideas:

• Use a mandatory token like OWNER_APIFY_TOKEN that will also act as a fallback to the current folder structure (so if the APIFY_TOKEN_{OWNER} is not found it will fall back to OWNER_APIFY_TOKEN
• Require a config json (maybe configurable on repo variables?) that will match the name of the actors to their owner and the name of the token (still in the env variable). So we could have

  { actor-name1: {
      owner: "organization1",
      token: "BUILD_TOKEN"
  }}

  This solution will also relax the strict condition on the folder structure for the monorepos, allowing to quickly change ownership on Apify of an account, without actually change anything codewise (but it would be a breaking change)