Resolve typing of stacked route definitions

[ahopkins]

Because of the weird necessity to return a route object for a static route, there is a RouteWrapper type that is meant to handle this use case. However, none of the convenience decorators (app.get, app.post, etc) will ever hit this use case. Therefore they can return RouteHandler.

This overly general typing was causing type annotation failures for this pattern, even though it is intentionally supported:

@app.get("/")
@app.post("/")
async def handler(request: Request):
    return json({"foo": "bar"})

This PR resolves the issue (even if not for app.route).

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (main@1668e15). Click here to learn what that means.
The diff coverage is 100.000%.

@@           Coverage Diff            @@
##             main     #2455   +/-   ##
========================================
  Coverage        ?   87.246%           
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  Files           ?        60           
  Lines           ?      5073           
  Branches        ?       907           
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  Hits            ?      4426           
  Misses          ?       476           
  Partials        ?       171           

Impacted Files	Coverage Δ
sanic/mixins/routes.py	92.800% <100.000%> (ø)

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