`NIX_REMOTE` appears to be a URL, but does not unescape the path

[roberth]

Describe the bug

While implementing relocated store support in nix-diff, I've found that it has a URL-like query parameters support.
However, the syntax is effectively undocumented.

Steps To Reproduce

$ NIX_REMOTE=/tmp/stores/foo%3Fbar? nix-store --init

$ ls /tmp/stores/
foo%3Fbar

Expected behavior

NIX_REMOTE is either a URL, not a URL, or something well specified.

nix-env --version output

Additional context

• URL handling tech debt #9603

Priorities

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[thufschmitt]

More precisely, it should point to https://nixos.org/manual/nix/stable/command-ref/conf-file#conf-store as it's just an old alias for it