feat: add request timing calculation for waterfall

[vigneshshanmugam]

• fix Values / calculations for receive / content downloading times seem too high  #166
• part of capture more network information to improve waterfall #152
• Adds the request timing calculations for all network events when --network flag is enabled. The output is expected to be in the format

{
  blocked: 0.8809999562799931,
  queueing: 0.49599993508309126,
  proxy: -1,
  dns: -1,
  ssl: -1,
  connect: -1,
  send: 0.1300000585615635,
  wait: 60.22300000768155,
  receive: 0.9560000617057085,
  total: 62.686000019311905
}

All of the data is in milliseconds and any missing data will be denoted with -1

[Kerry350]

👀👀👀

[apmmachine]

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Build stats

• Build Cause: Pull request #168 updated

• Start Time: 2020-12-10T13:36:39.313+0000

• Duration: 17 min 46 sec

Test stats 🧪

Test	Results
Failed	0
Passed	46
Skipped	0
Total	46

[Kerry350]

I've run this via the CLI against a few journeys and the values are looking much better 👍 (It'll also be massively beneficial to have these here vs in the UI).

It was still possible for me to see values that ran in to seconds when the journey contained multiple navigations. As an example against one specific asset prior to this PR I was getting a value of around 3 seconds consistently, with the changes here I'm seeing an average of 1 second. So it's much, much better. In Chrome dev tools that asset runs in the ms, so things still seem a little higher in certain scenarios, but I'm not confident enough to say something is actually "wrong".

[vigneshshanmugam]

@Kerry350 Thanks for the review. Yes it would be possible to see high values even in seconds for assets even with this PR when the assert is of type .gif, streaming downloads, progressive jpegs. In these cases the first byte arrives faster which means faster wait times (TTFB), but the content download takes a longer time.

Example gif - https://www.thebmc.co.uk/media/images/Banners/summit%20600x100px.gif

Running through our agent - different run not same one

val https://www.thebmc.co.uk/media/images/Banners/summit%20600x100px.gif {
  blocked: 0.5070000188425183,
  queueing: 1.1180000146850944,
  proxy: -1,
  dns: 0.7249999325722456,
  ssl: 606.307000038214,
  connect: 778.0400000046939,
  send: 0.27600000612437725,
  wait: 775.154999922961,
  receive: 1124.0200001047924,
  total: 2680.0800000783056
}