Clean up module documentation (#36909)

* Clean up module documentation

This PR includes:
- Removal of `default: None` (and variations)
- Removal of `required: false`
- Fixing booleans and `type: bool` where required

* Fix remaining (new) validation issues

lib/ansible/modules/cloud/atomic/atomic_container.py

@@ -33,22 +33,17 @@ options:
           - Define the backend to use for the container
         required: True
         choices: ["docker", "ostree"]
-        default: None
     name:
         description:
           - Name of the container
         required: True
-        default: null
     image:
         description:
           - The image to use to install the container
         required: True
-        default: null
     rootfs:
         description:
           - Define the rootfs of the image
-        required: False
-        default: null
     state:
         description:
           - State of the container
@@ -60,13 +55,10 @@ options:
           - Define if it is an user or a system container
         required: True
         choices: ["user", "system"]
-        default: None
     values:
         description:
             - Values for the installation of the container.  This option is permitted only with mode 'user' or 'system'.
               The values specified here will be used at installation time as --set arguments for atomic install.
-        required: False
-        default: None
 '''
 
 EXAMPLES = '''