Expose aggregate file sizes in FileStats

We're not sure that file counts are a good proxy for project size and
this will give us more direct insight.

src/server/scriptInfo.ts

@@ -316,6 +316,11 @@ namespace ts.server {
             return this.textStorage.version;
         }
 
+        /*@internal*/
+        getTelemetryFileSize() {
+            return this.textStorage.getTelemetryFileSize();
+        }
+
         /*@internal*/
         public isDynamicOrHasMixedContent() {
             return this.hasMixedContent || this.isDynamic;