feat(signer): add ERC2335 ProxyStore

[ManuelBilbao]

This PR implements a new way to safely store proxy keys using ERC-2335 format. It saves (and reads) the keys and secrets using the following structure:

├── PROXY_DIR_KEYS_ENV
│   └── <CONSENSUS_PUBLIC_KEY>
│       └── <MODULE_ID>
│           ├── bls/
│           │   ├── <PROXY_PUBLIC_KEY1>.json
│           │   ├── <PROXY_PUBLIC_KEY1>.sig
│           │   ├── <PROXY_PUBLIC_KEY2>.json
│           │   └── <PROXY_PUBLIC_KEY2>.sig
│           └── ecdsa/
│               ├── <PROXY_PUBLIC_KEY3>.json
│               └── <PROXY_PUBLIC_KEY3>.sig
└── <secrets_path>
    └── <CONSENSUS_PUBLIC_KEY>
        └── <MODULE_ID>
            ├── bls/
            │   ├── <PROXY_PUBLIC_KEY1>
            │   └── <PROXY_PUBLIC_KEY2>
            └── ecdsa
                └── <PROXY_PUBLIC_KEY3>

Storing in the .sig file the delegation signature

Close #71

[ltitanb]

While trying the full flow using the example in da_commit i get an error error: error sending request for url (http://127.0.0.1:20000/signer/v1/generate_proxy_key) although the request is received from the server.

I've also noticed that loading the keys is quite slow when running locally, so maybe we should add a /status endpoint in the signer server and wait on that when starting the other modules in the docker compose. This can also be used to add a health check in the container

[ManuelBilbao]

Added a healthcheck on docker compose so singer-dependant modules don't start until signer is healthy