Refactor error handling in data explorer Part 3 (#315)

- Make sure we pass the error message string instead of an error object when we call `TelemetryProcessor.traceFailure` since TelemetryProcessor will call `JSON.stringify` on the error object which would result in an empty object
- Removed ErrorParserUtility since it only works on specific error types. We can just log the full error message and manually derive information we need from the message.
- Added option to include stack trace in `getErrorMessage`. This is useful for figuring out where the client side script errors are coming from.
- Some minor refactors

src/Contracts/DataModels.ts

@@ -216,18 +216,6 @@ export interface UniqueKey {
   paths: string[];
 }
 
-// Returned by DocumentDb client proxy
-// Inner errors in BackendErrorDataModel when error is in SQL syntax
-export interface ErrorDataModel {
-  message: string;
-  severity?: string;
-  location?: {
-    start: string;
-    end: string;
-  };
-  code?: string;
-}
-
 export interface CreateDatabaseAndCollectionRequest {
   databaseId: string;
   collectionId: string;