Support for persistent $HOME directory

[AObuchow]

Description

It would be nice to have the /home/user directory persist across workspace startup/shutdown. $HOME Persistence would use the PVC strategy assigned to the DevWorkspace:

• When using the common/per-user PVC strategy, all workspaces would have their own unique home directory, that would be mounted to the common PVC under a different subpath
• When using the per-workspace PVC strategy, the workspace's home directory would exist on the workspace PVC
• When using the ephemeral PVC strategy, the workspace's home directory would not persist after the workspace is shutdown (no persistent storage)

I propose we add a new DWOC field config.workspace.persistentHomeUserDirectoryConfig:

config:
  workspace:
    persistentHomeUserDirectoryConfig:
      enabled: <bool>

Making a struct to hold the home directory config settings would allow us to add further configuration options in the future.
For example, if users end up requesting that workspaces should share their home directories (no sub-path) when using the common/per-user PVC strategy, we could add something like:

config:
  workspace:
    persistentHomeUserDirectoryConfig:
      enabled: <bool>
+     shareHomePerUser: <bool>

Additional context

Upstream Che Issue