Installer support for storage resource group and storage agent

## Things to do in the installers

To ease development and testing of frontend involving SFTP/filebrowser related features, we need to automate the initial configuration of them in development setups.

- Pull the sftp/filebrowser images and register them to the image metadata database. We could upload them to index.docker.io and let the installer perform the per-image rescan (#1621).
### For single-node all-in-one setup

- Prerequisite: #1672
- Just share the default resource group and agent with other sessions to run `DIRECT_ACCESS` sessions.
### For multi-node setup (with dedicated storage-proxy nodes)

- Prerequisite for flexible sharing of agent nodes: #496
- Create a dedicated resource group and configure it as follows:\* Update the storage volume access list (in the shared config) to include the default storage proxy volume.
- Allow execution of `DIRECT_ACCESS` sessions only.
- Allow all users to use this resource group.

- Create a dedicated agent configuration for agent(s) belonging to the above resource group.\* Set the host port range to match with the firewall configuration.

JIRA Issue: BA-180