feat(jans-pycloudlib): handle required files for external configuration backends

[iromli]

As we're supporting external configuration (secrets and configmaps), some of these backends need some files e.g. credentials, configuration, etc. With the new configuration schema, they can be stored and pulled directly from secrets/configmaps backend into the pod.

Goals:

• refactor AWS integration
• refactor Google integration
• refactor Vault integration