[TestRunner] create new test runner that takes configuration file

This CL lands the initial new run_test_suite.js that can take its
configuration from a config JSON file, or from flags.

This new script is only used to run `npm run auto-interactionstest`
and nothing more; I want to roll it out slowly and ensure that
everyone is aware of it before removing the old Python script. I will
create a doc with all the various steps, and required documentation,
as I've taken the chance to rename some options to make them clearer.

Bug: chromium:1186163
Change-Id: I5a199f82ac7ab0f323988acacaa7aae2d64e6349
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2763866
Commit-Queue: Jack Franklin <jacktfranklin@chromium.org>
Reviewed-by: Paul Lewis <aerotwist@chromium.org>
diff --git a/scripts/devtools_paths.js b/scripts/devtools_paths.js
index e8025ac..a433eb6 100644
--- a/scripts/devtools_paths.js
+++ b/scripts/devtools_paths.js
@@ -145,6 +145,10 @@
   return path.join(nodeModulesPath(), 'stylelint', 'bin', 'stylelint.js');
 }
 
+function mochaExecutablePath() {
+  return path.join(nodeModulesPath(), 'mocha', 'bin', 'mocha');
+}
+
 function downloadedChromeBinaryPath() {
   const paths = {
     'linux': path.join('chrome-linux', 'chrome'),
@@ -159,6 +163,7 @@
   nodePath,
   devtoolsRootPath,
   nodeModulesPath,
+  mochaExecutablePath,
   stylelintExecutablePath,
   downloadedChromeBinaryPath
 };