Remove loop as required listener arg

[ahopkins]

The main change of this PR is to remove loop as a required argument for listeners. In most cases now, loop should not be necessary. Both of the following will be acceptable:

@app.before_server_start
async def without(app):
    ...

@app.before_server_start
async def with(app, loop):
    ...

[codecov]

Codecov Report

Merging #2414 (5f07ad5) into main (44b108b) will increase coverage by 0.077%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##              main     #2414       +/-   ##
=============================================
+ Coverage   87.165%   87.243%   +0.077%     
=============================================
  Files           60        60               
  Lines         5010      5017        +7     
  Branches       904       904               
=============================================
+ Hits          4367      4377       +10     
+ Misses         470       468        -2     
+ Partials       173       172        -1     

Impacted Files	Coverage Δ
sanic/mixins/runner.py	95.744% <ø> (ø)
sanic/app.py	89.728% <100.000%> (+0.060%)	⬆️
sanic/models/handler_types.py	100.000% <100.000%> (ø)
sanic/server/events.py	100.000% <100.000%> (ø)
sanic/server/protocols/http_protocol.py	88.095% <0.000%> (+3.571%)	⬆️

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