Alternatate classes on instantiation for Config and Sanic.ctx

[ahopkins]

Resolves #2115

[Tronic]

Otherwise looks good.

[codecov]

Codecov Report

Merging #2119 (21811f3) into main (1a352dd) will increase coverage by 0.123%.
The diff coverage is 87.770%.

❗ Current head 21811f3 differs from pull request most recent head 2497871. Consider uploading reports for the commit 2497871 to get more accurate results

@@              Coverage Diff              @@
##              main     #2119       +/-   ##
=============================================
+ Coverage   92.133%   92.255%   +0.123%     
=============================================
  Files           38        38               
  Lines         3470      3525       +55     
  Branches       572       591       +19     
=============================================
+ Hits          3197      3252       +55     
  Misses         185       185               
  Partials        88        88               

Impacted Files	Coverage Δ
sanic/server.py	88.175% <33.333%> (ø)
sanic/__main__.py	82.143% <68.750%> (+7.143%)	⬆️
sanic/asgi.py	93.396% <75.000%> (-0.835%)	⬇️
sanic/response.py	94.231% <75.000%> (-0.506%)	⬇️
sanic/http.py	77.574% <80.000%> (+0.083%)	⬆️
sanic/reloader_helpers.py	75.385% <80.000%> (-0.025%)	⬇️
sanic/blueprint_group.py	96.721% <84.615%> (-3.279%)	⬇️
sanic/app.py	92.683% <100.000%> (+0.060%)	⬆️
sanic/base.py	100.000% <100.000%> (ø)
sanic/blueprints.py	100.000% <100.000%> (ø)
... and 9 more

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