Update cargo to 2024 edition (#842)

Some effects of this change:
- New formatting changes across many files. No functionality changes
should occur from that.
- Calls to `set_env` are considered unsafe, since this only happens in
tests we wrap them in `unsafe` blocks

codex-rs/execpolicy/src/main.rs

@@ -1,15 +1,15 @@
 use anyhow::Result;
 use clap::Parser;
 use clap::Subcommand;
-use codex_execpolicy::get_default_policy;
 use codex_execpolicy::ExecCall;
 use codex_execpolicy::MatchedExec;
 use codex_execpolicy::Policy;
 use codex_execpolicy::PolicyParser;
 use codex_execpolicy::ValidExec;
-use serde::de;
+use codex_execpolicy::get_default_policy;
 use serde::Deserialize;
 use serde::Serialize;
+use serde::de;
 use std::path::PathBuf;
 use std::str::FromStr;