Hummingbird marketplace, protobufs, CLI client, library functions

[rohrerj]

This PR contains:

• the marketplace in marketplace
• the marketplace CLI client in marketplace_client
• the protobufs in proto/hummingbird
• the marketplace library implementation in pkg/hummingbird/marketplace and pkg/hummingbird/registration
• the script to add a marketplace to the current topology in setup_marketplace.py
• a script to populate the database of the marketplace in populate_marketplace.py

TODO:

• Fix make gazelle for new connectrpc endpoints

---

This change is 

[juagargi]

The fix to make gazelle will come as part of some small refactors to this PR, on PR #70