Refactor filter/filter_with_hvg

[rcannood]

I think filter/filter_with_hvg is a misnomer because typically you don't want this component to filter, only annotate.

In addition, any references to "genes" should be renamed to features or vars.

Proposal:

highly_variable/highly_variable_scanpy/config.vsh.yaml:

functionality:
  name: highly_variable_scanpy
  namespace: highly_variable
  ...
  arguments:
    ...
    - name: "--var_name_filter"
      type: string
      default: "highly_variable"
      description: In which .var slot to store a boolean array corresponding to which features are highly variable.
    - name: "--varm_name"
      type: string
      default: "highly_variable"
      description: In which .varm slot to store additional output.