Feature: Hash sum validation for connectors

### Feature description

Conduit connectors are go-plugin clients, and go-plugin supports hash sum validations for those:

> // SecureConfig is used to configure a client to verify the integrity of an
// executable before running. It does this by verifying the checksum is
// expected. Hash is used to specify the hashing method to use when checksumming
// the file. The configuration is verified by the client by calling the
// SecureConfig.Check() function.
//
// The host process should ensure the checksum was provided by a trusted and
// authoritative source. The binary should be installed in such a way that it
// can not be modified by an unauthorized user between the time of this check
// and the time of execution.

Source: https://github.com/hashicorp/go-plugin/blob/master/client.go#L230-L239

This can be used to increase a Conduit operator's confidence that the plugins used haven't been tampered with.