Provide Python 3 API for Tool Meister, along with containerized Tool Data Sink & Tool Meister processes

[portante]

Let's consider how we can design APIs and layout containers for allowing services and deployments external to pbench to leverage the Tool Meister functionality first provided with the b0.70 release.

1. Python 3 API for registering a tool

2. Python 3 API for loading registered tools into a given Redis instance

3. Python 3 APIs for invoking starting and stopping tools

4. Containerized "Tool Meister" instance, which uses a set of environment variables to provide parameters for its operation (where to find the Redis Server and the key to use)

5. Containerized "Tool Data Sink" instance, which also uses environment variables ...

---

This should be some kind of API offered in the Python client module.

Originally posted by @portante in #2076 (comment)

---

We should make this part of the API for a "start" operation.

Originally posted by @portante in #2076 (comment)

[portante]

In some ways, this work is subsumed by the new signal implementation from PR cloud-bulldozer/benchmark-wrapper#305.