feat: implement the stacks client

[djordon]

Description

Closes #176.

One of the things that we need is to fetch all stacks blocks that have been anchored to a specific bitcoin block id/hash. The core of this PR adds the code to do that. Specifically, we:

• Fetch the stacks block IDs associated with a bitcoin block hash from the stacks API.
• Use the stacks block IDs to get the raw stacks Blocks from a stacks node.

Note that the code here uses the new /v3/blocks/[block ID] endpoint to get the raw block data from the stacks node. This endpoint only fetches Nakamoto blocks, so we cannot test this code path without running a Nakamoto stacks node.

Changes

This PR has the following changes:

1. Do chmod +x devenv/local/docker-compose/tests/devnet-liveness.sh
2. Update the docker-compose.local.yml to test out running a stacks node post-Nakamoto. These changes are intended to be removed/merged with our docker-compose devnet setup when we have Nakamoto running.
3. Updated our Dockerfiles to use the LABEL command instead of the deprecated MAINTAINER command.
4. Add code for the Stacks client implementation. This client is assumed to be configured from a config.yaml file, which right now is signer/src/config/default.toml.

Follow-up Changes

There are some caveats that need to be addressed in follow-up PRs. The big ones are:

1. I was unable to test the /v3/blocks/[block ID] endpoint! Getting Nakamoto to work locally has been challenging, so this PR doesn't have a working integration test. @jferrant pointed me to the docker-compose file in the stacks-regtest-env repo, which has what I need to get this over the finish line ([Feature]: Add integration tests for the Stacks Client #227).
2. Support more stacks-node and stacks-api endpoints in the config.toml ([Feature]: Support multiple Stacks node URLs #225).

Testing information

I tested one of the StacksClient functions using a locally running stacks setup. This function hits the stacks API for stacks block IDs. I was unable to test the function that fetches the nakamoto block given the stacks block ID.

[netrome]

Beautiful! I have a few comments and questions, but nothing that can't be tackled as a follow-up.