Fix lost response body data. Fixes #1166

[quinnj]

This creates one extra copy of the bytes instead of the view, but the result of readuntil is always being materialized as a String anyway, which was making a copy of the bytes before anyway (i.e. the behavior that changed was String(::View) copied the view bytes then made the string, and now we're explicitly making the copy and then the string is made).

[KristofferC]

Would be good with a new release with this fix since quite a few packages error on PkgEval with issues that are likely originating from this.

[fredrikekre]

https://github.com/JuliaRegistries/General/pull/105361

[quinnj]

Thanks @fredrikekre