Avoid most boxes in precompilation code (#57986)

- Use `local` where variable names accidentally overlapped and caused
boxes
- Use `@lock` to avoid closures
- Move out some recursive closures to top-level normal function to avoid
boxing them
- Use explicit boxes (`Ref`) instead of relying on the typeassert on the
`Core.Box` because it it hard to determine if a `Core.Box` is benign or
not.
- Only assign to `io` once to avoid boxing it.
- Type assert some `Tuple{Int, Int}` on `IO`.

The two remaining boxes after this is `t_print` and `monitor_std`.

(cherry picked from commit 4a3eba3)

Author: KristofferC