Fix over sanitization of user agents (microsoft#163665)

* Fix over sanitization of user agents

* Better user agent test

* Mix in common props after cleaning

* Update comments

Author: lramos15

src/vs/platform/telemetry/common/telemetryService.ts

@@ -110,15 +110,15 @@ export class TelemetryService implements ITelemetryService {
 
 		return this._commonProperties.then(values => {
 
-			// (first) add common properties
-			data = mixin(data, values);
-
-			// (next) add experiment properties
+			// add experiment properties
 			data = mixin(data, this._experimentProperties);
 
-			// (last) remove all PII from data
+			// remove all PII from data
 			data = cleanData(data as Record<string, any>, this._cleanupPatterns);
 
+			// add common properties
+			data = mixin(data, values);
+
 			// Log to the appenders of sufficient level
 			this._appenders.forEach(a => a.log(eventName, data));
 

src/vs/platform/telemetry/common/telemetryUtils.ts

@@ -286,6 +286,7 @@ export function getPiiPathsFromEnvironment(paths: IPathEnvironment): string[] {
  * @returns The cleaned stack
  */
 function anonymizeFilePaths(stack: string, cleanupPatterns: RegExp[]): string {
+
 	let updatedStack = stack;
 
 	const cleanUpIndexes: [number, number][] = [];