Add grep -> grep_v and grep_v -> grep mutations

lib/mutest/mutator/node/send.rb

@@ -37,6 +37,8 @@ class Send < self
           reverse_map:   %i[map each],
           reverse_merge: %i[merge],
           sample:        %i[first last],
+          grep:          %i[grep_v],
+          grep_v:        %i[grep],
           send:          %i[public_send __send__],
           shift:         %i[first],
           to_a:          %i[to_ary to_set],

meta/send.rb

@@ -784,3 +784,29 @@
   mutation 'a === self'
   mutation 'a.kind_of?(b)'
 end
+
+Mutest::Meta::Example.add :send do
+  source 'a.grep(b)'
+
+  singleton_mutations
+  mutation 'a'
+  mutation 'b'
+  mutation 'self.grep(b)'
+  mutation 'a.grep'
+  mutation 'a.grep(nil)'
+  mutation 'a.grep(self)'
+  mutation 'a.grep_v(b)'
+end
+
+Mutest::Meta::Example.add :send do
+  source 'a.grep_v(b)'
+
+  singleton_mutations
+  mutation 'a'
+  mutation 'b'
+  mutation 'self.grep_v(b)'
+  mutation 'a.grep_v'
+  mutation 'a.grep_v(nil)'
+  mutation 'a.grep_v(self)'
+  mutation 'a.grep(b)'
+end