Internal refactor

[Nukesor]

Part of #540 Fixes #548

This MR completely restructures the daemon's architecture and process related state handling.

The code is a lot cleaner and the MPSC between the message handlers and the task handler has been removed, effectively removing a lot of potential for deadlocks and moving a lot of task related logic closer to the message handler.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 74.41558% with 197 lines in your changes missing coverage. Please review.

Project coverage is 80.09%. Comparing base (a97448d) to head (0d9d5e3).

Files	Patch %	Lines
pueue/src/daemon/callbacks.rs	11.49%	77 Missing :warning:
pueue/src/daemon/task_handler.rs	74.57%	30 Missing :warning:
pueue/src/daemon/process_handler/finish.rs	73.62%	24 Missing :warning:
pueue/src/daemon/process_handler/spawn.rs	88.27%	17 Missing :warning:
pueue/src/daemon/process_handler/kill.rs	79.41%	14 Missing :warning:
pueue/src/daemon/network/message_handler/send.rs	0.00%	10 Missing :warning:
pueue/src/daemon/process_handler/start.rs	88.46%	6 Missing :warning:
pueue/src/daemon/network/message_handler/group.rs	82.75%	5 Missing :warning:
pueue/src/daemon/network/message_handler/kill.rs	62.50%	3 Missing :warning:
pueue/src/daemon/network/message_handler/mod.rs	84.21%	3 Missing :warning:
... and 6 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #547 +/- ## ========================================== - Coverage 80.25% 80.09% -0.16% ========================================== Files 77 75 -2 Lines 5666 5536 -130 ========================================== - Hits 4547 4434 -113 + Misses 1119 1102 -17 ```

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[github-actions[bot]]

Test Results

  3 files  ±0   22 suites  ±0   3m 0s :stopwatch: +8s 148 tests ±0  148 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0  316 runs  ±0  316 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0 

Results for commit 0d9d5e31. ± Comparison against base commit a97448de.

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