Configure Secret storage backend to be used with Local Hub

Description

As the secret storage backend has been implemented in #644, it should be consumed by Local Hub once the gRPC delegation is implemented (#645).

[x] Create dedicated Helm chart for secret storage backend.

NOTE: This chart can be installed multiple times with different configuration. Create it under: https://github.com/capactio/capact/tree/main/deploy/kubernetes/charts
[x] Add built-in option to install the dotenv storage. By default, disabled. (consider if this really simplify sth)
- Create proper Types and TypeInstances that will be created as a part of the installation
  - We want to create both the Helm release TypeInstances and TypeInstance describing installed storage.
- We can do it in the same fashion as we did for post-install-type-instance.yaml. The new job should be located in the newly created Helm chart for secret backend storage.
- We can do it as a part of populator or created it directly under /cmd/secret-storage-backend
[x] Add dedicated manifests (probably Action) to install AWS Secrets Manager.
- Create proper Types and TypeInstances that will be created as a part of the installation
- Uninstall is out of the scope.
[x] Updated secret backend storage: If only one provider is enabled, use it by default (context can be empty).
[x] Created dedicated documentation on our website under storage backend section:

See epic #604 for the reason and use cases.