Optimize template (#28044)

* Optimize template

* In fixing template to handle diff correctly #24477, I introduced more
  round trips to the remote end which slowed things down  The new code now
  uses one fewer round trips than the old code.
* Reimplement a large part of template by calling the copy action plugin
  instead of doing it in template's code.  This reduces the code in
  template and gives us one place to fix bugs and optimize.
* Add a follow parameter to template that mirrors the follow parameters
  for file and copy.
* Fix copy's diff handling (probably broken in my rewrite for in 2.4
  development)
* Adjusted when copy creates tmp dirs to rduce round trips in copy and
  template.

Fixes #27956

lib/ansible/modules/files/template.py

@@ -81,6 +81,13 @@ options:
         if the destination does not exist.
     type: bool
     default: 'yes'
+  follow:
+    description:
+      - This flag indicates that filesystem links in the destination, if they exist, should be followed.
+      - Previous to Ansible 2.4, this was hardcoded as C(yes).
+    type: bool
+    default: 'no'
+    version_added: "2.4"
 notes:
   - For Windows you can use M(win_template) which uses '\r\n' as C(newline_sequence).
   - Including a string that uses a date in the template will result in the template being marked 'changed' each time