This is better for privacy and to avoid leaking netrc credentials in a
MITM attack, but also the assumption that we check the hash no longer
holds in some cases (in particular for impure derivations).
Partially reverts 5db358d4d7.
(cherry picked from commit c04bc17a5a0fdcb725a11ef6541f94730112e7b6)
(cherry picked from commit f2f47fa725fc87bfb536de171a2ea81f2789c9fb)
(cherry picked from commit 7b39cd631e0d3c3d238015c6f450c59bbc9cbc5b)
Upstream-PR: https://github.com/NixOS/nix/pull/11585
Change-Id: Ia973420f6098113da05a594d48394ce1fe41fbb9