Ensure users don't have root access in container-based Workspaces

Context

Discussion originally happened in #391856 (comment 1284825444)

MR - Set the user id, group id and file system group... (!119138 - merged)

What

Ensure the security context for a container is set so that users cannot escape and gain privilege. We'll have to figure out what are the best default values which are restrictive enough without creating a hurdle for most use-cases. Are the default values for the security context enough?

How

Set the pod-overrides and container-overrides before saving the processed devfile to the database to set the default/safe values for user ID, group ID, file system group ID, etc. (i.e. security context settings)

Availability and Testing

Ensure updated test coverage in unit/integration/feature tests.