Make interprocess polling interval configurable (#16560)

As recently there was back-and-forth with this hardcoded value
(0.001 -> 0.01 -> 0.005), obviousely the optimal value for it depends on
Ansible usage scanario and is better to be configurable.

This patch adds a new config option in DEFAULT section,
`internal_poll_interval`, with default of 0.001 corresponding to the
value hardcoded in Ansible v2.1.
This config option is then used instead of hardcoded values where
needed.

Related GH issue: 14219

lib/ansible/plugins/strategy/free.py

@@ -21,6 +21,7 @@ __metaclass__ = type
 
 import time
 
+from ansible import constants as C
 from ansible.errors import AnsibleError
 from ansible.playbook.included_file import IncludedFile
 from ansible.plugins import action_loader
@@ -202,7 +203,7 @@ class StrategyModule(StrategyBase):
                 display.debug("done adding collected blocks to iterator")
 
             # pause briefly so we don't spin lock
-            time.sleep(0.001)
+            time.sleep(C.DEFAULT_INTERNAL_POLL_INTERVAL)
 
         # collect all the final results
         results = self._wait_on_pending_results(iterator)