[WIP] Orchestration

**Important note:** This pull request is a work in progress (WIP). Please do **not** merge it until "[WIP]" is removed from the PR title.

The intent of this WIP PR is to solicit feedback on the PHP API of Orchestration early and often.

The first set of commits will be non-functional code samples for Orchestration. Please review these as they come in and provide feedback. The goal of this exercise to design the Orchestration PHP API from the perspective of a developer using this API.

Once the PHP API is finalized via code samples, the next set of commits to follow will be documentation of the API. Specifically, these will be a Quickstart Guide and a Complete User Guide.

Once the documentation commits have been reviewed and finalized, the final set of commits to this PR will be the tests and actual implementation of the API, that is the various classes under the `OpenCloud\Orchestration` namespace.

Once the tests and implementation have been reviewed and finalized, this PR will no longer be WIP. At this point, it may be merged.