Support YAML anchors in configs for `CLI`

[rusmux]

🚀 Feature request

Support YAML anchors in configs for CLI.

Motivation

Anchors reduce duplication of configuration values. For example (not necessarily like this):

x-common-args: &common_args
  a: 1
  b: 2
  c: 3

instances:
  - class_path: __main__.MyClass
    init_args:
      name: instance_1
      <<: *common_arg
  - class_path: __main__.MyClass
    init_args:
      name: instance_2
      <<: *common_arg
  ...

Pitch

YAML anchors are supported by CLI.

Alternatives