inject a dictionary of avaiable variables and the environment into executor

Expose vars & env as a dictionary (as hostvars is done) so that a template can be used to debug a playbook by dumping relevant data structures,

Enables this action:

    - name: dump everything
      local_action: template 
         src=common/templates/dump.j2 
         dest=./ansible_data_dump.txt 

along with this template:

    Module Variables ("vars"):
    --------------------------------
    {{ vars | to_nice_json }} 
    
    Environment Variables ("environment"):
    --------------------------------
    {{ environment | to_nice_json }} 

    GROUP NAMES Variables ("group_names"):
    --------------------------------
    {{ group_names | to_nice_json }}

    GROUPS Variables ("groups"):
    --------------------------------
    {{ groups | to_nice_json }}
    
    HOST Variables ("hostvars"):
    --------------------------------
    {{ hostvars | to_nice_json }} 
    
To dump a list of relevant data structures in the context of a template, or in a playbook.