Implement customer [de]serialization for IntegerInterner

Added some basic tests that the representation of the interner
is only the `values` sequence, and that it round-trips successfully.

cranelift/peepmatic/crates/runtime/Cargo.toml

@@ -18,6 +18,8 @@ serde = { version = "1.0.105", features = ["derive"] }
 thiserror = "1.0.15"
 wast = { version = "15.0.0", optional = true }
 
+[dev-dependencies]
+serde_test = "1.0.114"
 
 [features]
 # Enable support for a few extra methods that are required by the `peepmatic`