Fix typo, remove redundant paragraph

Fixes #12437

Fixes #12427

Python 3: there's no xrange

Support «hosts: foo[1:]» and add tests for split/apply_subscript

Now, instead of relying on hostvars on the executor side, we compile
the vars for the delegated to host in a special internal variable and
have the PlayContext object look for things there when applying task/
var overrides, which is much cleaner and takes advantage of the code
already dealing with all of the magic variable variations.

Fixes #12127
Fixes #12079

* Clearing interpreter settings from variables, so those set for the
  original host aren't incorrectly applied to the delegated to host
* Fixed incorrect string for remote user in delegated hosts hostvars
* Properly looking for multiple possiblities in the delegated-to hosts
  hostvars (ansible_ssh_host vs. ansible_host)

Fix example formatting in the documentation

added new module object to vca

initial add of vca common module

fixes #12434

Use six.moves.range instead (aliased to xrange on Python 2, aliased to
range on Python 3).

Also I couldn't resist replacing the elaborate chr/ord/randrange dance
with the simpler random.choice(string.ascii_lowercase) that was already
used elsewhere in the Ansible codebase.

Fixes #12349

Allow env-setup to use spaces in full path

Same fix as was applied in f162990c to the action plugin

Fixes #12355

Tested.  Thanks for spotting and then fixing this -- Allow hexadecimal ranges in IPv6 addresses, not only 0-9

Remove deprecation warning; now handled in _split_patterns

The earlier distinction was never used; .ipv6_address was always a copy
of .ipv4_address, and the latter was always used to set the remote_addr
field in the PlayContext.

Also uses the canonical ansible_host/ansible_port names when setting the
address and port from variables.

More tests, better handling of list arguments to _split_pattern