This commit adds a new counterpart to `ComponentMain` which accepts
an options struct for specifying callback functions. Currently it
supports `construct` (for components) and `call` (for methods), but is
extensible in a non-breaking fashion in future to support all other
provider methods as they become useful to implement.
The original `ComponentMain` still exists, though it may be desirable to
deprecate it in future in favor of `MainWithOptions`.
Adds initial support for resource methods (via a new `Call` gRPC method similar to `Invoke`), with support for authoring methods from Node.js, and calling methods from Python.
