Suggestion: Allow chaining groups

[RuiNtD]

It would be nice if specifying groups in other groups would work. In 0.25.0, this (partial) config file causes an error:

groups:
  default:
    - mc
  mc:
    - prism
    - atlauncher

pwsh> resticprofile snapshots
2024/02/10 16:54:05 using configuration file: c:\restic\profiles.yaml
2024/02/10 16:54:05 cannot load profile 'mc': not found