[MM-20353] Change KVSetWithOptions to accept a byte slice (#13213)

* Drop EncodeJSON from PluginKVSetOptions

* Add unit tests for KVSetWithOptions with nil values

i18n/en.json

@@ -5254,10 +5254,6 @@
     "id": "model.plugin_kvset_options.is_valid.old_value.app_error",
     "translation": "Invalid old value, it shouldn't be set when the operation is not atomic."
   },
-  {
-    "id": "model.plugin_kvset_options.serialize_value.app_error",
-    "translation": "Could not deserialize a value. EncodeJSON: {{.EncodeJSON}}."
-  },
   {
     "id": "model.post.is_valid.channel_id.app_error",
     "translation": "Invalid channel id"