add namespace param for fn and env (#2556)

This PR moves fission CLI as closer as possible to kubectl command behaviour.  We have improved namespace handling behaviour across CLI.

* add namespace param for fn and env
* use common fn for ns check
* update validation
* default namespace for httpTrigger, env and package, config and triggers
* use default ns
* add namespace filter to spec
* add forceNamespace flag
* set current namespace
* add default namespace in config
* add namespace specific destroy
* add all namespace in the list of resources
* add namespace as global tag
* use %s instead of %v
* add test cases for namespace
* use ns in get all functions

test/kind_CI.sh

@@ -101,6 +101,10 @@ main() {
         $ROOT/test/tests/test_fn_update/test_secret_update.sh \
         $ROOT/test/tests/test_fn_update/test_nd_pkg_update.sh \
         $ROOT/test/tests/test_fn_update/test_poolmgr_nd.sh  
+        $ROOT/test/tests/test_namespace/test_ns_current_context.sh
+        $ROOT/test/tests/test_namespace/test_ns_flag.sh
+        $ROOT/test/tests/test_namespace/test_ns_env.sh
+        $ROOT/test/tests/test_namespace/test_ns_deprecated_flag.sh
 
     set -e