Add toml inventory plugin (#41593)

* First pass at a toml inventory

* Make EXAMPLES yaml

* Remove unnecessary comment

* Small formatting changes

* Add ansible-inventory option to list as TOML

* TOML inventory improvements, to allow a more simple inventory, specifically related to children

* changelog

* Simplify logic

* Dedupe _expand_hostpattern, making it available to all inventory plugins

* Don't make the TOML inventory dependent on the YAML inventory

* Quote IP address values

* Add more TOML examples

* Further cleanups

* Enable the toml inventory to run by default

* Create toml specific dumper

* 2.8

* Clean up imports

* No toml pygments lexer

* Don't raise an exception early when toml isn't present, and move toml to the end, since it requires an external dep

* Require toml>=0.10.0

* Further clean up of empty data

* Don't require toml>=0.10.0, but prefer it, add code for fallback in older versions

* Ensure we actually pass an encoder to toml.dumps

* Simplify recursive data converter

* Appease tests, since we haven't limited controller testing to 2.7+

* Update docstring for convert_yaml_objects_to_native

* remove outdated catching of AttributeError

* We don't need to catch ImportError when import ansible.plugins.inventory.toml

* Add note about what self.dump_funcs.update is doing

* Address some things

* A little extra comment

* Fix toml availability check

* Don't create an intermediate list

* Require toml file extension

* Add metadata

* Remove TOML docs from intro_inventory to prevent people from getting the wrong idea

* It's in defaults, remove note

* core supported, indicate very clearly that this is preview status

lib/ansible/config/base.yml

@@ -1408,7 +1408,7 @@ INVENTORY_ANY_UNPARSED_IS_FAILED:
   version_added: "2.7"
 INVENTORY_ENABLED:
   name: Active Inventory plugins
-  default: ['host_list', 'script', 'yaml', 'ini', 'auto']
+  default: ['host_list', 'script', 'yaml', 'ini', 'toml', 'auto']
   description: List of enabled inventory plugins, it also determines the order in which they are used.
   env: [{name: ANSIBLE_INVENTORY_ENABLED}]
   ini: