Add Usage Telemetry

[karlseguin]

Sends basic usage telemetry. Final URL will need to be changed (probably).

Added Telemetry section to readme (please review). And I the Privacy Policy (linked from the readme) might need updating to reflect this collection?

Currently, most things need an Allocator and Loop to run. Now we also need a Telemetry, and it isn't hard to imagine a not-so-distant future where various parts also need access to a Config. Rather than adding more and more parameters, I've introduced an App which is meant to group global data into a single variable, so that future additions are less likely to require touching so much code. Besides this change, the Telemetry code is relatively standalone.

[karlseguin]

Another good reason to replace std.http.Client is just how impossible it is to test.

[krichprollsch]

@karlseguin after discussion, here is what we could add for the navigate event:

{
  "iid": "ffffffff-ffff-ffff-ffff-ffffffffffff",
  "version": "7b0e725",
  "arch": "x86_64",
  "os": "linux",
  "mode": "serve",
  "driver": "cdp",
  "event": "navigate"

  "tls": true,
  "proxy": false, // is a proxy configured for the request, always false for now.
}