Wait for new process to ACK before termination of old on restart

[ahopkins]

Current logic terminates a process (sends SIGINT), then starts a new process. This PR reverses the order so that it starts the new process, waits for ACK and then sends the SIGINT.

Closes #2619

[codecov]

Codecov Report

Base: 88.568% // Head: 88.483% // Decreases project coverage by -0.085% ⚠️

Coverage data is based on head (f83553b) compared to base (92e7463).
Patch coverage: 95.081% of modified lines in pull request are covered.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #2623       +/-   ##
=============================================
- Coverage   88.568%   88.483%   -0.086%     
=============================================
  Files           81        81               
  Lines         6631      6660       +29     
  Branches      1129      1135        +6     
=============================================
+ Hits          5873      5893       +20     
- Misses         522       527        +5     
- Partials       236       240        +4     

Impacted Files	Coverage Δ
sanic/worker/process.py	89.565% <91.666%> (+0.801%)	⬆️
sanic/application/ext.py	100.000% <100.000%> (ø)
sanic/config.py	97.402% <100.000%> (+0.051%)	⬆️
sanic/constants.py	100.000% <100.000%> (ø)
sanic/log.py	100.000% <100.000%> (ø)
sanic/mixins/startup.py	90.909% <100.000%> (+0.020%)	⬆️
sanic/worker/manager.py	93.442% <100.000%> (+0.522%)	⬆️
sanic/app.py	89.071% <0.000%> (-0.729%)	⬇️
sanic/server/websockets/impl.py	37.788% <0.000%> (-0.692%)	⬇️

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[ahopkins]

Going to put this on hold until #2626 is in. Using the new pattern there, we can remove this from a config setting and do it as a command feature.