feat(persistent): Redesign CommitStateSpace, bound Commit lifetime (#2534)

This PR updates the relrc dependency to v0.5.0 and completely redesigns
the `CommitStateSpace` struct. The result is much cleaner:

- `PersistentHugr` is an immutable data type following the design of the
types of the [`im` crate](https://docs.rs/im/latest/im/), i.e. it is a
mutable Rust type that is cheap to clone and mutate (immutability -- if
desired -- is achieved by cloning before mutating).
- `Commit` is a "transaction", i.e. one atomic mutation that was applied
to a `PersistentHugr`. It has an ID, obtainable through `commit.id()`
and a lifetime parameter that ensures it does not stay in scope beyond
the lifetime of the `PersistentHugr`
- Each `PersistentHugr` belongs to a unique `CommitStateSpace`. A
`CommitStateSpace` is a registry of all commits of the `PersistentHugr`s
within that state space. It keeps the map between commits and IDs.

This is a breaking change, but does not trigger a breaking HUGR release
because it is hidden behind an unstable feature.

Author: lmondada

Cargo.lock

@@ -89,7 +89,7 @@ pest_derive = "2.8.2"
 pretty = "0.12.5"
 pretty_assertions = "1.4.1"
 zstd = "0.13.2"
-relrc = "0.4.6"
+relrc = "0.5.0"
 wyhash = "0.6.0"
 
 # These public dependencies usually require breaking changes downstream, so we

Cargo.toml

@@ -39,4 +39,4 @@ bench = false
 rstest.workspace = true
 semver.workspace = true
 serde_with.workspace = true
-insta.workspace = true
+insta = { workspace = true, features = ["yaml"] }