Add support for listener and signal prioritization

[ahopkins]

The purpose of this PR is to add priority to listeners and signals.

Requires: sanic-org/sanic-routing#76
Blocks: sanic-org/sanic-ext#228

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (160ec7a) 88.217% compared to head (e8f2cd8) 88.232%.

Files	Patch %	Lines
sanic/app.py	81.818%	1 Missing and 1 partial ⚠️
sanic/mixins/listeners.py	94.736%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #2822       +/-   ##
=============================================
+ Coverage   88.217%   88.232%   +0.014%     
=============================================
  Files           93        93               
  Lines         7282      7291        +9     
  Branches      1251      1253        +2     
=============================================
+ Hits          6424      6433        +9     
+ Misses         600       599        -1     
- Partials       258       259        +1     

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