The tempdir crate has been superseded by tempfile.

Bump [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Fixes #169

Alternative to #144.

This reduces the duration to glob `**/*.rs` in a rustc checkout on my PC
from ~1000ms to ~820ms:
```
Benchmark 1: ./local
  Time (mean ± σ):     822.0 ms ±  11.2 ms    [User: 272.5 ms, System: 549.2 ms]
  Range (min … max):   811.8 ms … 849.6 ms    10 runs
 
Benchmark 2: ./upstream
  Time (mean ± σ):      1.019 s ±  0.006 s    [User: 0.468 s, System: 0.551 s]
  Range (min … max):    1.005 s …  1.026 s    10 runs
 
Summary
  ./local ran
    1.24 ± 0.02 times faster than ./upstream
```

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>