Fix for ServerError obscured by ServerParseError

[dillontiner]

Fixes #8945 where not handling the response status code before parsing the response body text causes the apollo client to send a ServerParseError when it should send a ServerError.

The changes here are taken from #8974 which has been inactive for months

[apollo-cla]

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[jpvajda]

@dillontiner Thanks for follow up on this and our apologies for the lingering PR review, we'll check this out soon. 🙏

[jpvajda]

This LGTM but I'm going to ask another person on the team to give this a quick check. cc @hwillson @alessbell @MrDoomBringer @benjamn

Once merged we can close out:

• Parse http response #8945
• Fix for ServerError and ServerParseError occurring at the same time. #8974

[jpvajda]

This seems to be failing the NPM Bundle Size check

[MrDoomBringer]

LGTM. I went ahead and added some extra tests - we're now testing unparsable JSON with both 200 and 400 server response codes. Other than that, I'm glad to get this merged! Thanks a ton @TakahiroHimi for the original PR and @dillontiner for keeping the fix alive.

All the best,
Emmanuel, Intern :-)