TODO: paging results

* Fixes hostvar serialization issue (#12005)
* Fixes regression in include_vars from within a role (#9498), where
  we had the precedence order for vars_cache (include_vars, set_fact)
  incorrectly before role vars.
* Fixes another bug in which vars loaded from files in the format of
  a list instead of dictionary would cause a failure.

Fixes #9498
Fixes #12005

Use PBKDF2HMAC() from cryptography for vault keys.

moved mandatory back to filters as it does not always return a boolean, it does an exception on failure

Remove unused (copied) _before_comment method

This was copied from inventory/ini.py, but the rewritten version doesn't
use it, and shows that it isn't needed.

Rewrite inventory/ini.py

Now we accept IPv6 addresses _with port numbers_ only in the standard
[xxx]:NN notation (though bare IPv6 addresses may be given, as before,
and non-IPv6 addresses may also be placed in square brackets), and any
other host identifiers (IPv4/hostname/host pattern) as before, with an
optional :NN suffix.

Based on a patch by @Richard2ndQuadrant.

(There's no compelling reason to do this right now, but should be parser
need to be called multiple times in future, this makes it easier.)

The new code parses INI-format inventory files in a single pass using a
well-documented state machine that reports precise errors and eliminates
the duplications and inconsistencies and outright errors in the earlier
three-phase parsing code (e.g. three ways to skip comments). It is also
much easier now to follow what decisions are being taken on the basis of
the parsed data. The comments point out various potential improvements,
particularly in the area of consistent IPv6 handling.

On the ornate marble tombstone of the old code, the following
inscription is one last baffling memento from a bygone age:

-    def _before_comment(self, msg):
-        ''' what's the part of a string before a comment? '''
-        msg = msg.replace("\#","**NOT_A_COMMENT**")
-        msg = msg.split("#")[0]
-        msg = msg.replace("**NOT_A_COMMENT**","#")
-        return msg

Add win_splitdrive filter for windows users

Update faq

Guru is not a thing any more.

Don't convert nulls to strings.

Update dependencies for pywinrm

This change is similar to https://github.com/ansible/ansible/pull/10465

It extends the logic there to also support none types.  Right now if you have
a '!!null' in yaml, and that var gets passed around, it will get converted to
a string.

eg. defaults/main.yml
```
ENABLE_AWESOME_FEATURE: !!null # Yaml Null
OTHER_CONFIG:
  secret1: "so_secret"
  secret2: "even_more_secret"

CONFIG:
  hostname: "some_hostname"
  features:
    awesame_feature: "{{ ENABLE_AWESOME_FEATURE}}"
  secrets: "{{ OTHER_CONFIG }}"
```

If you output `CONFIG` to json or yaml, the feature flag would get represented in the output
as a string instead of as a null, but secrets would get represented as a dictionary.  This is
a mis-match in behaviour where some "types" are retained and others are not.  This change
should fix the issue.

I also updated the template test to test for this and made the changes to v2.

Added a changelog entry specifically for the change from empty string to null as the default.

Made the null representation configurable.

It still defaults to the python NoneType but can be overriden to be an emptystring by updating
the DEFAULT_NULL_REPRESENTATION config.

cloudstack: fixes and consistency change

Make get_group run in O(n*log(n)) instead of O(n^2) by using a cache (#9437 rebase)