Support True Multicast: Single Source to Multiple Destinations in a Single Connection

## Tell us about the problem you're trying to solve
Currently, if I need to sync the same data from a source to multiple destinations, I have to define multiple Connections. For example, I might need to sync Salesforce data to BigQuery for analysis and Postgres for application access. I can reuse the Source configuration but each Connection entails a separate request to the Source API for the same data. This results in higher load on my Airbyte cluster and an unnecessary depletion of my API quota leading to higher costs.

## Describe the solution you’d like
The Airbyte protocol already supports the standard exchange of information between a Source and Destination and Sources and Destinations are run independent of one another. Provide the ability to specify multiple destinations for a single Connection and run them with a single Source instance that passes the same data to both (or N) Destinations.

## Describe the alternative you’ve considered or used
Create a separate Connection for every Source/Destination combination.

## Additional context
N/A

## Are you willing to submit a PR?
Don't think I can.