… fails to resolve (#1525)

Flask and Quart are deprecating and removing the ``_xxx_ctx_stack``s
and adopting a more direct usage of ContextVars. The previous code
will therefore break for the latest version of Quart and start to warn
for Flask and then break.

This fix should work with any version of Flask or Quart, and hence is
a more robust version. There is an extra indirection, however I don't
think this is on any hot path.

Co-authored-by: Anton Pirker <anton.pirker@sentry.io>

…1312)

Uses environment markers according to PEP 508. 

The current constraint expresses at least urllib3 version 1.10.0,
which has at least 5 CVEs open.

Projects relying on `sentry-sdk` will get an optimistic version of
the latest, so current test suites are already using the latest version
which patches these vulnerabilities.

Refs:

- GHSA-www2-v7xj-xrc6 (critical)
- GHSA-mh33-7rrq-662w (high)
- GHSA-hmv2-79q8-fv6g (high)
- GHSA-wqvq-5m8c-6g24 (moderate)
- GHSA-5phf-pp7p-vc2r (moderate)

* Run Tox in parallel

* Fixed patching of middlewares to fix the 'coroutine' error for non existent routes.

* Only capture server errors

* Fixed form POST in FastApiIntegration.

* Fixed form uploads on starlette projects

* Fixed error while handling 404 errors.

* Fix error during handling of form validation error.

* Find the correct handler (for classes with parent classes

* Do not call starlette integration, because it needs to be set in the init()