feat(CodeArtifact): add option to provide aws credentials directly

[Khartris]

TLDR: This PR adds the option to declare AWS credentials directly instead of pulling them from a profile.

Background: We have a project where we need two sets of AWS credentials for our e2e tests (one is for us and one is for our customer). Locally we have two profiles for them, but in our gitlab CI we inject these via environment variables. When I tried to add this plugin to our project I encountered the problem that it only accepts profiles for selecting the correct credentials. This works fine locally but in our CI the plugin simply takes the default credentials from the environment variables which are the wrong ones. As our CI has no profiles we cannot select the correct credentials with this plugin. My solution is to add the option to directly declare the accessKeyId and secretAccessKey in the configuration (e.g. via environment variables).