bpo-38614: Add timeout constants to test.support (GH-16964)

Add timeout constants to test.support:

* LOOPBACK_TIMEOUT
* INTERNET_TIMEOUT
* SHORT_TIMEOUT
* LONG_TIMEOUT
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index b745490..184c67c 100755
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -37,7 +37,6 @@
 HOST = support.HOST
 # test unicode string and carriage return
 MSG = 'Michael Gilfix was here\u1234\r\n'.encode('utf-8')
-MAIN_TIMEOUT = 60.0
 
 VSOCKPORT = 1234
 AIX = platform.system() == "AIX"
@@ -2527,7 +2526,7 @@
 
     # Time in seconds to wait before considering a test failed, or
     # None for no timeout.  Not all tests actually set a timeout.
-    fail_timeout = 3.0
+    fail_timeout = support.LOOPBACK_TIMEOUT
 
     def setUp(self):
         self.misc_event = threading.Event()
@@ -4320,7 +4319,7 @@
         self.addCleanup(signal.signal, signal.SIGALRM, orig_alrm_handler)
 
     # Timeout for socket operations
-    timeout = 4.0
+    timeout = support.LOOPBACK_TIMEOUT
 
     # Provide setAlarm() method to schedule delivery of SIGALRM after
     # given number of seconds, or cancel it if zero, and an
@@ -4610,7 +4609,7 @@
 
         self.event.set()
 
-        read, write, err = select.select([self.serv], [], [], MAIN_TIMEOUT)
+        read, write, err = select.select([self.serv], [], [], support.LONG_TIMEOUT)
         if self.serv not in read:
             self.fail("Error trying to do accept after select.")
 
@@ -4638,7 +4637,7 @@
 
         self.event.set()
 
-        read, write, err = select.select([conn], [], [], MAIN_TIMEOUT)
+        read, write, err = select.select([conn], [], [], support.LONG_TIMEOUT)
         if conn not in read:
             self.fail("Error during select call to non-blocking socket.")
 
@@ -5838,8 +5837,7 @@
     FILESIZE = (10 * 1024 * 1024)  # 10 MiB
     BUFSIZE = 8192
     FILEDATA = b""
-    # bpo-37553: This is taking longer than 2 seconds on Windows ARM32 buildbot
-    TIMEOUT = 10 if sys.platform == 'win32' and platform.machine() == 'ARM' else 2
+    TIMEOUT = support.LOOPBACK_TIMEOUT
 
     @classmethod
     def setUpClass(cls):
@@ -5865,7 +5863,7 @@
         support.unlink(support.TESTFN)
 
     def accept_conn(self):
-        self.serv.settimeout(MAIN_TIMEOUT)
+        self.serv.settimeout(support.LONG_TIMEOUT)
         conn, addr = self.serv.accept()
         conn.settimeout(self.TIMEOUT)
         self.addCleanup(conn.close)
@@ -6369,7 +6367,7 @@
 
 
 class CreateServerFunctionalTest(unittest.TestCase):
-    timeout = 3
+    timeout = support.LOOPBACK_TIMEOUT
 
     def setUp(self):
         self.thread = None