Add option to suppress grammar rendering

A new flag
.. namedconf:statement::
   :suppress_grammar:
suppresses pretty-printing grammar.

It is useful mostly for zones because each zone has it's own grammar, so
printing all of them at once usually does not make sense.

(cherry picked from commit 1f5bc4fe3b)

doc/arm/_ext/iscconf.py

@@ -96,6 +96,7 @@ def domain_factory(domainname, domainlabel, todolist, grammar):
                 "tags": lambda arg: split_csv(arg, required=False),
                 # one-sentece description for use in summary tables
                 "short": directives.unchanged_required,
+                "suppress_grammar": directives.flag,
             }
 
             @property
@@ -237,6 +238,8 @@ def domain_factory(domainname, domainlabel, todolist, grammar):
                         union_flags = union_flags.union(
                             set(one_grammar_dict.subgrammar.get("_flags", []))
                         )
+                    if "suppress_grammar" in self.options:
+                        continue
                     grammarnode = self.format_grammar(multi_grammar, grammar_grp)
                     contentnode.insert(0, grammarnode)
 

doc/arm/reference.rst

@@ -6178,6 +6178,7 @@ Here is an example of a typical split DNS setup implemented using
 ``zone`` Statement Grammar
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 .. namedconf:statement:: zone
+   :suppress_grammar:
 
 .. _zone_statement:
 
@@ -6191,6 +6192,7 @@ Here is an example of a typical split DNS setup implemented using
 Zone Types
 ^^^^^^^^^^
 .. namedconf:statement:: type
+   :suppress_grammar:
 
    The ``type`` keyword is required for the ``zone`` configuration unless
    it is an ``in-view`` configuration. Its acceptable values are: