Accessing the `Zone` variable without checking if it's defined or not
leads to an error "Zone is not defined" if zone.js is not imported (nooped).
This commit adds an additional check before getting the current zone where
the `doRequest` is being called.
PR Close#51119
Having the request run in the angular zone has the consequence of triggering the CD for every read of the response stream.
This commit wraps the whole `doRequest` to run outside angular with every callback on the observer being called inside the zone.
Fixes#50979.
PR Close#50981
This commit introduces a new `HttpBackend` implentation which makes requests using the fetch API
This feature is a developer preview and is opt-in.
It is enabled by setting the providers with `provideHttpClient(withFetch())`.
NB: The fetch API is experimental on Node but available without flags from Node 18 onwards.
PR Close#50247
