UX: Show users SRI hashes everywhere instead of base32

This is *just* in output messages that look relatively like the FOD
failure message. It's not great that we inconsistently use the old
format in random places.

Change-Id: I4b9ce73a98a3a50c924cfe1d7cded42f3756df6b

doc/manual/rl-next/sri-hash-output.md

@@ -0,0 +1,8 @@
+---
+synopsis: "Consistently use SRI hashes in hash mismatch errors"
+cls: [2868]
+category: Improvements
+credits: jade
+---
+Previously there were a few weird cases (flake inputs, e.g., among others) where Lix would print the old Nix base-32 hash format (sha256:abcd...) rather than the newer [SRI base64 format](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity) (sha256-AAAA...) that is used in most Lix hash mismatch errors.
+This made it annoying to compare them to hashes shown by most of the modern UI surface of Lix which uses SRI.