Draft: Add toxiproxy service and add a proxy on object store

What does this Merge Request do and why?

First iteration of #1513.

This adds the following:

1. toxiproxy-server component as part of gdk
2. a proxy named object_store_proxy to proxy requests to object_store

Remaining todo for this MR:

• configure clients to use object_store proxy port
• create the proxy during gdk start. The server is running, but no object_store_proxy yet.
• Document toxiproxy dependency installation

Out of scope:

1. Configuring toxics on object_store_proxy. This still needs to be done manually through toxiproxy-cli.

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.

Closes #1513