Add integration test for running a query

In order to do this, needed to add a few extra pieces:

* extracted the simple database download so that it only happens
  once and is shared across all tests.
* needed to update mocha to latest version since that has the new API
* But typings isn't updated yet, so submitted a PR into DefinitelyTyped
  for that.
* Added a concept of helper files for test runs. These helper files
  will contain all the shared global setup.

Unfortunately, at this point, we can't run using a language pack since
we would also need to download the the ql repository from somewhere.

Author: aeisenberg

extensions/ql-vscode/gulpfile.ts/index.ts

@@ -6,5 +6,5 @@ import { compileView } from './webpack';
 import { packageExtension } from './package';
 
 export const buildWithoutPackage = gulp.parallel(compileTypeScript, compileTextMateGrammar, compileView, copyTestData, copyViewCss);
-export { compileTextMateGrammar, watchTypeScript, compileTypeScript };
+export { compileTextMateGrammar, watchTypeScript, compileTypeScript, copyTestData };
 exports.default = gulp.series(exports.buildWithoutPackage, packageExtension);

extensions/ql-vscode/gulpfile.ts/tests.ts

@@ -1,6 +1,17 @@
 import * as gulp from 'gulp';
 
 export function copyTestData() {
+  copyNoWorkspaceData();
+  copyCliIntegrationData();
+  return Promise.resolve();
+}
+
+function copyNoWorkspaceData() {
   return gulp.src('src/vscode-tests/no-workspace/data/**/*')
     .pipe(gulp.dest('out/vscode-tests/no-workspace/data'));
 }
+
+function copyCliIntegrationData() {
+  return gulp.src('src/vscode-tests/cli-integration/data/**/*')
+    .pipe(gulp.dest('out/vscode-tests/cli-integration/data'));
+}