Use a random temporary file name for `visudo`

[pvdrz]

Describe the changes done on this pull request This PR uses a random name for the temporary file created by visudo. This file is put in the /tmp directory.

It also updates the tests that involve the name of this file to use snapshots so we can filter the random part of the filename from it.

Pull Request Checklist

• [x] I have read and accepted the code of conduct for this project.
• [x] I have tested, formatted and ran clippy over my changes.
• [x] I have commented and documented my changes.
• [ ] This pull request will fix issue https://github.com/memorysafety/sudo-rs/issues/<#issue> where a proper discussion about a solution has taken place.

[github-actions[bot]]

Number of dependencies and binary size impact report

Metric	main	PR #669	Delta
Direct dependencies	3	3	-
Total dependencies	4	4	-
Binary size	992.2 KiB	992.3 KiB	-
Text size	577.6 KiB	577.8 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: -0.11 :warning:

Comparison is base (d58920d) 57.86% compared to head (296f3c3) 57.76%.

:exclamation: Current head 296f3c3 differs from pull request most recent head 2e783fd. Consider uploading reports for the commit 2e783fd to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #669 +/- ## ========================================== - Coverage 57.86% 57.76% -0.11% ========================================== Files 68 68 Lines 8941 8955 +14 ========================================== - Hits 5174 5173 -1 - Misses 3767 3782 +15 ``` | [Impacted Files](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/669?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety) | Coverage Δ | | |---|---|---| | [src/visudo/cli.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/669?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL3Zpc3Vkby9jbGkucnM=) | `0.00% <0.00%> (ø)` | | | [src/visudo/help.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/669?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL3Zpc3Vkby9oZWxwLnJz) | `0.00% <0.00%> (ø)` | | | [src/visudo/mod.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/669?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 [1 file with indirect coverage changes](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/669/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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