[httpx] replace searx.poolrequests by searx.network

settings.yml:

* outgoing.networks:
   * can contains network definition
   * propertiers: enable_http, verify, http2, max_connections, max_keepalive_connections,
     keepalive_expiry, local_addresses, support_ipv4, support_ipv6, proxies, max_redirects, retries
   * retries: 0 by default, number of times searx retries to send the HTTP request (using different IP & proxy each time)
   * local_addresses can be "192.168.0.1/24" (it supports IPv6)
   * support_ipv4 & support_ipv6: both True by default
     see https://github.com/searx/searx/pull/1034
* each engine can define a "network" section:
   * either a full network description
   * either reference an existing network

* all HTTP requests of engine use the same HTTP configuration (it was not the case before, see proxy configuration in master)

searx/testing.py

@@ -10,8 +10,8 @@ import traceback
 
 from os.path import dirname, join, abspath, realpath
 
-from unittest import TestCase
 from splinter import Browser
+import aiounittest
 
 
 class SearxTestLayer:
@@ -82,7 +82,7 @@ def run_robot_tests(tests):
             test(browser)
 
 
-class SearxTestCase(TestCase):
+class SearxTestCase(aiounittest.AsyncTestCase):
     """Base test case for non-robot tests."""
 
     layer = SearxTestLayer