Improve sentry reports w/out context

[pjenvey]

Some sentry reports lack context due to twisted Failures not including a traceback.

One cause is twisted.web.client's _WrapperException which wraps other exceptions (possibly even multiple exceptions) and commonly lack a tb. We should special case these: log their wrapped exceptions instead, which'll likely include a context.

e.g. ResponseNeverReceived is one:
https://sentry.prod.mozaws.net/operations/autopush-prod/issues/345377/

There's others without a tb for unknown reasons:
https://sentry.prod.mozaws.net/operations/autopush-prod/issues/345112/events/8063796/

We can special case the logger to forcefully include the current stack trace when coming across these. That might provide enough context to track down their cause so we can improve their handling.

[pjenvey]

Er, before special casing _WrapperExceptions inside the logger itself, let's ensure they're all trapped/handled for all our twisted.web.client calls. So they never propagate down to the logger in the first place.

(The logger special casing might still be useful in case we forget to handle new ones in the future).