bpo-34542: Update test certs and keys (GH-8997) (GH-9007)

Update all test certs and keys to use future proof crypto settings:

* 3072 bit RSA keys
* SHA-256 signature

Signed-off-by: Christian Heimes <christian@python.org>
(cherry picked from commit e6dac0077996b1e1f886f036d6f2606237fa4c85)
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
index 5c22630..49a4d72 100644
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -61,9 +61,9 @@
                (('localityName', 'Castle Anthrax'),),
                (('organizationName', 'Python Software Foundation'),),
                (('commonName', 'localhost'),)),
-    'notAfter': 'Jan 17 19:09:06 2028 GMT',
-    'notBefore': 'Jan 19 19:09:06 2018 GMT',
-    'serialNumber': 'F9BA076D5B6ABD9B',
+    'notAfter': 'Aug 26 14:23:15 2028 GMT',
+    'notBefore': 'Aug 29 14:23:15 2018 GMT',
+    'serialNumber': '98A7CF88C74A32ED',
     'subject': ((('countryName', 'XY'),),
              (('localityName', 'Castle Anthrax'),),
              (('organizationName', 'Python Software Foundation'),),
@@ -86,9 +86,9 @@
     'issuer': ((('countryName', 'XY'),),
             (('organizationName', 'Python Software Foundation CA'),),
             (('commonName', 'our-ca-server'),)),
-    'notAfter': 'Nov 28 19:09:06 2027 GMT',
-    'notBefore': 'Jan 19 19:09:06 2018 GMT',
-    'serialNumber': '82EDBF41C880919C',
+    'notAfter': 'Jul  7 14:23:16 2028 GMT',
+    'notBefore': 'Aug 29 14:23:16 2018 GMT',
+    'serialNumber': 'CB2D80995A69525C',
     'subject': ((('countryName', 'XY'),),
              (('localityName', 'Castle Anthrax'),),
              (('organizationName', 'Python Software Foundation'),),
@@ -334,6 +334,8 @@
 
             self.assertNotEqual(child_random, parent_random)
 
+    maxDiff = None
+
     def test_parse_cert(self):
         # note that this uses an 'unofficial' function in _ssl.c,
         # provided solely for this test, to exercise the certificate