[docs] Add CI matrix and script (#5461)

* Rename CI jobs from ubuntu to ubuntu16

* Add CI matrix and script

tests/scripts/md-table/table.md.j2

@@ -0,0 +1,15 @@
+# CI test coverage
+
+To generate this Matrix run `./tests/scripts/md-table/main.py` 
+
+{%- for container_engine in container_engines %}
+
+## {{ container_engine }}
+
+| OS / CNI |{% for cni in network_plugins %} {{ cni }} |{% endfor %}
+|---|{% for cni in network_plugins %} --- |{% endfor %}
+{%- for os in operating_systems %}
+{{ os }} | {% for cni in network_plugins %} {{ ':white_check_mark:' if exists(container_engine, cni, os) else ':x:' }} |{% endfor %}
+{%- endfor %}
+
+{%- endfor %}