specgen: generate specification from connector.yaml

[hariso]

Feature description

!!! Should be merged only when the SDK is released!

The generated connector.yml is embedded in the connector binary and is used to create the specifications of the connector. The Source and Destination structs don't have to implement Parameters anymore, although the functions are kept for backwards compatibility.

See #3 in ConduitIO/conduit#1522.

[raulb]

@hariso I think this one can be closed.

[lovromazgon]

@raulb why do you think it can be closed? The related PR is still open and will remain so until we release the new SDK.

[raulb]

@lovromazgon sorry for late (missed this notification until now). Thought it could be closed because the originally attached PR was closed, but it seems that the PR closing this issue is this other instead.