Support API Keys for Authentication

[rjulian]

Right now, the terraform provider solely allows authentication via username and password to Aqua.

For organizations that leverage SSO or prefer to use API keys over user identities, it would be incredibly helpful to support API keys within the provider.

This would most clearly require a change to the client code, as right now we're getting a bearer token for the user and using it for all future requests, whereas making calls with the API tokens requires generation of an hmac signature including the request body.