PLT-4990 - Server: Split out channel permissions to Create/Manage/Delete (#4864)

* Server side changes.

* Fix unit tests and default config.

config/config.json

@@ -49,8 +49,12 @@
         "CustomDescriptionText": "",
         "RestrictDirectMessage": "any",
         "RestrictTeamInvite": "all",
+        "RestrictPublicChannelCreation": "all",
+        "RestrictPrivateChannelCreation": "all",
         "RestrictPublicChannelManagement": "all",
         "RestrictPrivateChannelManagement": "all",
+        "RestrictPublicChannelDeletion": "all",
+        "RestrictPrivateChannelDeletion": "all",
         "UserStatusAwayTimeout": 300,
         "MaxChannelsPerTeam": 2000,
         "MaxNotificationsPerChannel": 1000