urldecode filter for Jinja2 (#28503)

* urldecode filter for Jinja2

We needed this in order to deconstruct correct URLs using Jinja2.
And we might as well upstream this.

* Add integration tests

* Fixes for Python 3

* Add urlencode for older Jinja2

test/integration/targets/filters/tasks/main.yml

@@ -169,6 +169,19 @@
       - _bad_urlsplit_filter is failed
       - "'unknown URL component' in _bad_urlsplit_filter.msg"
 
+- name: Test urldecode filter
+  set_fact:
+    urldecoded_string: key="@{}é&%£ foo bar '(;\<>""°)
+
+- name: Test urlencode filter
+  set_fact:
+    urlencoded_string: '{{ urldecoded_string|urlencode }}'
+
+- name: Verify urlencode en urldecode
+  assert:
+    that:
+    - urldecoded_string == urlencoded_string|urldecode
+
 - name: Flatten tests
   block:
     - name: use flatten