Fixes and improvements (#257)

* Relate `ConfigurableProp` with its subtypes

  This change turns the `ConfigurableProp` type
  into a union of all its subtypes (e.g.
  `ConfigurablePropInteger`, `ConfigurablePropString`, etc.).

  This allows users to refer to that generic type
  when calling methods such as `components.reloadProps`
  and process the response by using a parent type. This
  is a better experience since users don't have to
  know in advance about the types of every single prop
  that's returned by the method.

* Custom component listing

  This change accepts an extra parameter when listing
  components, so that users can list private components,
  public/registry components, or both.

* Project management endpoints

  This change adds support for managing projects
  via the SDK. Users can now create, retrieve,
  update, and delete projects programmatically.

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Co-authored-by: Jay Vercellone <jay@pipedream.com>