Issue #24657: Prevent CGIRequestHandler from collapsing the URL query

Initial patch from Xiang Zhang. Also fix out-of-date _url_collapse_path() doc
string.
diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
index d50a9ac..6e5f2db 100644
--- a/Lib/test/test_httpservers.py
+++ b/Lib/test/test_httpservers.py
@@ -565,6 +565,13 @@
             (b'a=b?c=d' + self.linesep, 'text/html', 200),
             (res.read(), res.getheader('Content-type'), res.status))
 
+    def test_query_with_continuous_slashes(self):
+        res = self.request('/cgi-bin/file4.py?k=aa%2F%2Fbb&//q//p//=//a//b//')
+        self.assertEqual(
+            (b'k=aa%2F%2Fbb&//q//p//=//a//b//' + self.linesep,
+             'text/html', 200),
+            (res.read(), res.getheader('Content-type'), res.status))
+
 
 class SocketlessRequestHandler(SimpleHTTPRequestHandler):
     def __init__(self):