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]

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

Additional details and impacted files

@@            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]

Test Results

  3 files  ±0   22 suites  ±0   3m 0s ⏱️ +8s
148 tests ±0  148 ✅ ±0  0 💤 ±0  0 ❌ ±0 
316 runs  ±0  316 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 0d9d5e3. ± Comparison against base commit a97448d.

♻️ This comment has been updated with latest results.