Support editing task priorities

[jch-13]

Adds support for the modification of task priorities in a queue via pueue edit --priority/-o and pueue restart --edit-priority/-o (fixes #449). Despite the interesting discussion in #449 about how to improve task editing in general, this takes the easy way out and tries to integrate with the existing editing system by using (multiple) editor instances for now.

Checklist

• [x] I picked the correct source and target branch.
• [x] I included a new entry to the CHANGELOG.md.
• [x] I checked cargo clippy and cargo fmt. The CI will fail otherwise anyway.
• [x] (If applicable) I added tests for this feature or adjusted existing tests.
• [x] (If applicable) I checked if anything in the wiki needs to be changed.

[codecov[bot]]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (fb6caab) 79.61% compared to head (42af45a) 79.67%.

Files	Patch %	Lines
pueue/src/client/cli.rs	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #490 +/- ## =============================================== + Coverage 79.61% 79.67% +0.05% =============================================== Files 77 77 Lines 5538 5564 +26 =============================================== + Hits 4409 4433 +24 - Misses 1129 1131 +2 ```

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[github-actions[bot]]

Test Results

  2 files  ±0   14 suites  ±0   1m 23s :stopwatch: +7s 146 tests +2  146 :white_check_mark: +2  0 :zzz: ±0  0 :x: ±0  167 runs  +2  167 :white_check_mark: +2  0 :zzz: ±0  0 :x: ±0 

Results for commit 42af45a2. ± Comparison against base commit fb6caabb.

:recycle: This comment has been updated with latest results.

[jch-13]

Thank you! :)

[Nukesor]

Thanks :)