[MM-36444] Manage config deprecations for 6.0 (#18035)

* removing deprecated stuff

* removing deprecations and marking others for deprecations

* removing some of the configs

* partially remove ExperimentalChannelOrganization

* fixing merge issues

* moving default permissions to defaultroles function

* removing experimentaltownsquare

* removing old tests and remove legacysidebar config

* fixing test

* removing log

* removing unused variables

* MM-36444: Fix for renamed functions.

* MM-36444: go mod tidy and go mod vendor.

* MM-36444: Vendored go modules.

* MM-36444: Removes UseExperimentalGossip config field from model.

* Fix vendors

* fixing test

Co-authored-by: Benjamin Cooke <benjamincooke@Benjamins-MacBook-Pro.local>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Martin Kraft <martin@upspin.org>
Co-authored-by: Claudio Costa <cstcld91@gmail.com>

tests/test-config.json

@@ -19,7 +19,6 @@
         "EnableIncomingWebhooks": true,
         "EnableOutgoingWebhooks": true,
         "EnableCommands": true,
-        "EnableOnlyAdminIntegrations": true,
         "EnablePostUsernameOverride": false,
         "EnablePostIconOverride": false,
         "EnableLinkPreviews": false,
@@ -45,9 +44,6 @@
         "WebserverMode": "gzip",
         "EnableCustomEmoji": false,
         "EnableEmojiPicker": true,
-        "RestrictCustomEmojiCreation": "all",
-        "RestrictPostDelete": "all",
-        "AllowEditPost": "always",
         "PostEditTimeLimit": -1,
         "TimeBetweenUserTypingUpdatesMilliseconds": 5000,
         "EnablePostSearch": true,
@@ -57,22 +53,17 @@
         "EnableUserStatuses": true,
         "ExperimentalEnableAuthenticationTransfer": true,
         "ClusterLogTimeoutMilliseconds": 2000,
-        "CloseUnusedDirectMessages": false,
         "EnablePreviewFeatures": true,
         "EnableTutorial": true,
         "EnableOnboardingFlow": true,
         "ExperimentalEnableDefaultChannelLeaveJoinMessages": true,
         "ExperimentalGroupUnreadChannels": "disabled",
-        "ImageProxyType": "",
-        "ImageProxyURL": "",
-        "ImageProxyOptions": "",
         "EnableAPITeamDeletion": false,
-        "ExperimentalEnableHardenedMode": false,
+        "ExperimentalEnableHardenedMode": false
     },
     "TeamSettings": {
         "SiteName": "Mattermost",
         "MaxUsersPerTeam": 50,
-        "EnableTeamCreation": true,
         "EnableUserCreation": true,
         "EnableOpenServer": false,
         "EnableUserDeactivation": false,
@@ -81,23 +72,12 @@
         "CustomBrandText": "",
         "CustomDescriptionText": "",
         "RestrictDirectMessage": "any",
-        "RestrictTeamInvite": "all",
-        "RestrictPublicChannelManagement": "all",
-        "RestrictPrivateChannelManagement": "all",
-        "RestrictPublicChannelCreation": "all",
-        "RestrictPrivateChannelCreation": "all",
-        "RestrictPublicChannelDeletion": "all",
-        "RestrictPrivateChannelDeletion": "all",
-        "RestrictPrivateChannelManageMembers": "all",
-        "EnableXToLeaveChannelsFromLHS": false,
         "UserStatusAwayTimeout": 300,
         "MaxChannelsPerTeam": 2000,
         "MaxNotificationsPerChannel": 1000,
         "EnableConfirmNotificationsToChannel": true,
         "TeammateNameDisplay": "username",
         "ExperimentalEnableAutomaticReplies": false,
-        "ExperimentalHideTownSquareinLHS": false,
-        "ExperimentalTownSquareIsReadOnly": false,
         "ExperimentalPrimaryTeam": ""
     },
     "ClientRequirements": {