Add a receiveMultipleVideoStreams flag. (#2056)

* Add a receiveMultipleVideoStreams flag.

modules/flags/FeatureFlags.js

      *
      * @param {boolean} flags.runInLiteMode - Enables lite mode for testing to disable media decoding.
      * @param {boolean} flags.sourceNameSignaling - Enables source names in the signaling.
+     * @param {boolean} flags.receiveMultipleVideoStreams - Signal support for receiving multiple video streams.
      */
     init(flags) {
         this._runInLiteMode = Boolean(flags.runInLiteMode);
 
         this._sourceNameSignaling = Boolean(flags.sourceNameSignaling);
+        this._receiveMultipleVideoStreams = Boolean(flags.receiveMultipleVideoStreams);
         this._sendMultipleVideoStreams = Boolean(flags.sendMultipleVideoStreams);
         this._ssrcRewriting = Boolean(flags.ssrcRewritingOnBridgeSupported);
 
         return this._sourceNameSignaling && this._sendMultipleVideoStreams && this._usesUnifiedPlan;
     }
 
+    /**
+     * Checks if receiving multiple video streams is supported.
+     *
+     * @returns {boolean}
+     */
+    isReceiveMultipleVideoStreamsSupported() {
+        return this._receiveMultipleVideoStreams;
+    }
+
     /**
      * Checks if the run in lite mode is enabled.
      * This will cause any media to be received and not decoded. (Directions are inactive and no ssrc and ssrc-groups

modules/xmpp/xmpp.js

             logger.info('Source-name signaling is enabled');
             this.caps.addFeature('http://jitsi.org/source-name');
         }
+        if (FeatureFlags.isReceiveMultipleVideoStreamsSupported()) {
+            logger.info('Receiving multiple video streams is enabled');
+            this.caps.addFeature('http://jitsi.org/receive-multiple-video-streams');
+        }
 
         if (FeatureFlags.isSsrcRewritingSupported()) {
             logger.info('SSRC rewriting is supported');

types/auto/modules/flags/FeatureFlags.d.ts

      *
      * @param {boolean} flags.runInLiteMode - Enables lite mode for testing to disable media decoding.
      * @param {boolean} flags.sourceNameSignaling - Enables source names in the signaling.
+     * @param {boolean} flags.receiveMultipleVideoStreams - Signal support for receiving multiple video streams.
      */
     init(flags: any): void;
     _runInLiteMode: boolean;
     _sourceNameSignaling: boolean;
+    _receiveMultipleVideoStreams: boolean;
     _sendMultipleVideoStreams: boolean;
     _ssrcRewriting: boolean;
     _usesUnifiedPlan: any;
      * @returns {boolean}
      */
     isMultiStreamSupportEnabled(): boolean;
+    /**
+     * Checks if receiving multiple video streams is supported.
+     *
+     * @returns {boolean}
+     */
+    isReceiveMultipleVideoStreamsSupported(): boolean;
     /**
      * Checks if the run in lite mode is enabled.
      * This will cause any media to be received and not decoded. (Directions are inactive and no ssrc and ssrc-groups