treewide: fsm -> riff inside code -- DS-280

[cole-h]

Draft, because I'd like https://github.com/DeterminateSystems/riff/pull/58 to merge first (and I'll rebase on that) to prevent making more work for others.

[linear[bot]]

DS-276 Rename to `riff`

Any user-presenting references to `fsm` should be changed to `riff`. Bonus points for updating the code to match.

DS-280 Rename code references to `riff` as well

But after everything in-flight is done / merged, so as to reduce merge conflicts.

[Hoverbear]

Noting this requires some changes on the registry:

❯ riff run ls
✓ 🦀 rust: cargo, openssl, pkg-config, rustc, rustfmt
  2022-08-30T17:05:06.987170Z ERROR riff::dependency_registry: Could not parse new registry data from https://riff-registry.fly.dev/riff-registry.json, err: EOF while parsing a value at line 1 column 0
    at src/dependency_registry/mod.rs:104

Cargo.lock  Cargo.toml  LICENSE  README.md  dev-env  flake.lock  flake.nix  img  nix  registry  result  result-man  src  target

[Hoverbear]

Nice PR!

I managed to catch one you might have missed in a merge:

❯ rg fsm
src/dependency_registry/mod.rs
27:        "Reading cached registry (Maybe you need to remove `$XDG_CACHE_DIR/fsm/registry.json`?)"

[grahamc]

regarding the registry update: I fixed that issue by deploying the current registry code :).