feat: Retry requests in more situations

[bengourley]

This flips the retry logic from a flag that says "retry me", to a flag that says "don't retry me" –
and only if the "don't retry me" flag exists do we not retry. A couple of test cases are added for
new cases where we now retry, such as socket timeouts and socket hangups.

Also TIL:

Assigning a property on process.env will implicitly convert the value to a string.

Source: Node.js Process docs

So the env vars that are set in testing which are expected to be integers are now parsed as such.

[sazap10]

Whilst the change seems fine to me, after doing some testing it doesn't seem to be behaving as I would expect it to. Starting the upload whilst the upload server is not running and starting the upload server within the retry limit causes an "ESOCKETTIMEDOUT" error even if the upload server is running correctly. I don't know whether its request which is the issue or the server.

[bengourley]

Big update to this PR.

In investigating the issue mentioned by @sazap10 I ripped out request and replaced it with the send() implementation in bugsnag-build-reporter since that implementation was working in bugsnag/bugsnag-build-reporter-node#5 – it just uses the built-in http/https modules.

Because this library does multipart uploads I had to use the form-data module in addition (which was already included as a transistive dependency of request). It still was failing and I managed to track it down to the fact that prepareRequest() was making a single readstream to consume the source map file data which was being reused across attempts – meaning the data was consumed by the first attempt and there was nothing to be sent on subsequent attempts.

The fix is to call prepareRequest() every time a retry is attempted.

Since I went to the effort of removing request – it's quite a bloaty library – I think it makes sense to leave it out as we simply don't need it.

[sazap10]

SFTM, works fine with the upload server not being available when starting the upload and becoming available within the retry window.