MM-8853: Adding MANAGE_EMOJIS and MANAGE_OTHERS_EMOJIS permissions (#8860)

* MM-8853: Adding MANAGE_EMOJIS and MANAGE_OTHERS_EMOJIS permissions

* MM-8853: Removing unnecesary emoji enterprise feature

* Create emojis migration

* Adding MANAGE_EMOJIS and MANAGE_OTHERS_EMOJIS always to system admins

* Simplifing permissions checks

* Revert "Simplifing permissions checks"

This reverts commit e2cafc1905fc9e20125dd9a1552d2d0c7340ae59.

store/sqlstore/upgrade.go

@@ -425,6 +425,10 @@ func UpgradeDatabaseToVersion410(sqlStore SqlStore) {
 }
 
 func UpgradeDatabaseToVersion50(sqlStore SqlStore) {
+	// This version of Mattermost includes an App-Layer migration which migrates from hard-coded emojis configured
+	// in `config.json` to a `Permission` in the database. The migration code can be seen
+	// in the file `app/app.go` in the function `DoEmojisPermissionsMigration()`.
+
 	// TODO: Uncomment following condition when version 5.0.0 is released
 	//if shouldPerformUpgrade(sqlStore, VERSION_4_10_0, VERSION_5_0_0) {