Model Experiments: Add button to MLflow usage example

The following discussion from !174825 (merged) should be addressed:

• @a_akgun started a discussion: (+1 comment)

  @AndrasHerczeg the python experiment usage modal only appears on empty state, but on model registry we also have it in the action bar menu. WDYT if we open a followup issue for 17.8 to do the same?