Dev/gulp4

[bmoers]

Originally designed to only upgrade to gulp4 this change grew a little bigger.

• ATF tests & suites can now be passed to the gulp command e.g.

  npm run gulp testApp --  \
  --suites c67f38472f122854d8455aab2799b6c5,2d8b65dbdbf32300fcf41780399619b1 \
  --on-host https://dev00000.service-now.com/

• Test results of Parent / Child ATF Suite combination are displayed correctly (requires latest CICD integration app)

[bmoers]

@g-matharu can you pls review?