Compute entrypoints manifest

[shramee]

New computed field on Contract in manifest...

      contract.computed = [
        // For `#[computed]`
        {
          "contract": "actions",
          "entrypoint": "entrypoint_name",
          "component": null
        },
        // For `#[computed(ModelName)]`
        {
          "contract": "actions",
          "entrypoint": "entrypoint_name",
          "component": "ModelName"
        }
      ];

⚠️ At the moment only FreeFunctions are supported (not the ones in impl).

[tarrencev]

Minor feedback but generally looks good