Add support for decrypting encrypted secrets in remote development module

Issue: Add support for decrypting encrypted secrets in... (gitlab-org/gitlab#416898 - closed)

Add support for decrypting encrypted secrets in place in remote development module.

The key used to decryption is expected to be passed along with the encrypted secrets. It is not persisted in Kubernetes.

The different types of resources(secret key, encrypted secrets, basic, etc.) are differentiated by an annotation. If the annotation is missing, it is assumed to be "basic" resource i.e. the current set of resources that are sent by Rails - Deployment, Service, PVC, NetworkPolicy.

Rails MR: Allow creating workspaces for private projects (gitlab-org/gitlab!124273 - merged)

Old description

Issue: Spike: GA4K: Decrypt data sent by rails to agen... (gitlab-org/gitlab#414420 - closed)

Spike: Add support for multiple inventories and encrypted secrets in remote development module

Rails MR: Allow creating workspaces for private projects (gitlab-org/gitlab!124273 - merged)

This branch is based on top of Add support for multiple inventory resources an... (!1015 - merged) which has been moved out from this MR to get it merged independently so as to make this MR as small as possible.