Rewrite tox config (#9666)

* rewrite tox config

* fix apacheconftest-with-pebble deps

* more fixes

* more fixes

* move comment up

* fix mock location

* bump cffi

* update oldest constraints

* Revert "fix mock location"

This reverts commit 561037bfad.

* fix apache test

* fix server cleanup

* fix some leaky sockets

* stop leaking sockets

* change less

* Update tox.ini

Co-authored-by: alexzorin <alex@zorin.id.au>

* Update tox.ini

Co-authored-by: alexzorin <alex@zorin.id.au>

* tweak contributing doc

---------

Co-authored-by: alexzorin <alex@zorin.id.au>

tools/pinning/oldest/pyproject.toml

@@ -48,7 +48,7 @@ apacheconfig = "0.3.2"
 asn1crypto = "0.24.0"
 boto3 = "1.15.15"
 botocore = "1.18.15"
-cffi = "1.9.1"
+cffi = "1.11.5"
 chardet = "3.0.4"
 cloudflare = "1.5.1"
 configobj = "5.0.6"