add API key support in Hermes and Benchmarks clients

[bearmigiano]

• Fix bug which returns a new http client instead of the configured one
• Refactoring clients to use shared HTTP base client

[ewokndor]

This lgtm. Just one note:
If we are going to deploy this into k8s, then we might be required to load passwords from file, not env vars. You might want to consider supporting this right away.

[ewokndor]

However, note that the tests are not passing

[bearmigiano]

@ewokndor good point in general, but I think it doesn't apply here: this module isn't a deployable, atm it's just a dependency consumed by autobera, so nothing here ever runs in k8s on its own.
The API key only shows up in the tests (via env var for CI); the library itself just takes the key as a config string.

[ewokndor]

Do we actually run real tests against pyth? Because this would require to add the API_KEY just for tests? That feels awkward, if that is what's happening, we should mock the according test.

[ewokndor]

Unless there's a reason for it which I am not seeing.

[ewokndor]

OK the client just calls pyth and nothing else, test makes no sense without

[ewokndor]

OK the client just calls pyth and nothing else, test makes no sense without