Delete temporary directory when visudo is terminated

[pvdrz]

This PR changes visudo so it deletes the temporary directory once visudo exits or is terminated by a signal

[github-actions[bot]]

Number of dependencies and binary size impact report

Metric	main	PR #715	Delta
Direct dependencies	3	3	-
Total dependencies	4	4	-
Binary size	1003.4 KiB	1003.7 KiB	-
Text size	587 KiB	586.5 KiB	-

Dependencies diff

```diff └─ sudo-rs [v0.2.0-dev.20230711] ├─ glob [v0.3.1] ├─ libc [v0.2.147] └─ log [v0.4.19] ```

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: -1.52% :warning:

Comparison is base (60fe0ce) 57.39% compared to head (c7acce4) 55.87%. Report is 24 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #715 +/- ## ========================================== - Coverage 57.39% 55.87% -1.52% ========================================== Files 68 69 +1 Lines 9123 9369 +246 ========================================== - Hits 5236 5235 -1 - Misses 3887 4134 +247 ``` | [Files Changed](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/715?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety) | Coverage Δ | | |---|---|---| | [src/sudoers/mod.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/715?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL3N1ZG9lcnMvbW9kLnJz) | `79.01% <0.00%> (-7.84%)` | :arrow_down: | | [src/visudo/mod.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/715?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL3Zpc3Vkby9tb2QucnM=) | `0.00% <0.00%> (ø)` | | ... and [6 files with indirect coverage changes](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/715/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety)

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