[SOUP] Increase maximum connection limit from 17 to 256

https://bugs.webkit.org/show_bug.cgi?id=260725

Reviewed by Carlos Garcia Campos.

A long time ago, web browsers limited themselves to fairly small maximum
connection limits. Nowadays, Chrome uses 256 and Firefox uses 900, but
we still have a 17 connection limit established in 170917@main. I picked
17 for no other reason than that was what other browsers were doing at
the time. That reasoning is as good now as ever, so time to increase.

Note this has little effect on HTTP/2 and newer, as there we generally
use only one or two connections total per origin.

* Source/WebCore/platform/network/soup/SoupNetworkSession.cpp:
(WebCore::SoupNetworkSession::SoupNetworkSession):

Canonical link: https://commits.webkit.org/267455@main

Source/WebCore/platform/network/soup/SoupNetworkSession.cpp

@@ -97,11 +97,8 @@ class HostTLSCertificateSet {
 SoupNetworkSession::SoupNetworkSession(PAL::SessionID sessionID)
     : m_sessionID(sessionID)
 {
-    // Values taken from http://www.browserscope.org/ following
-    // the rule "Do What Every Other Modern Browser Is Doing". They seem
-    // to significantly improve page loading time compared to soup's
-    // default values.
-    static const int maxConnections = 17;
+    // These values match Chrome 81. https://stackoverflow.com/a/30064610
+    static const int maxConnections = 256;
     static const int maxConnectionsPerHost = 6;
 
     m_soupSession = adoptGRef(soup_session_new_with_options(