examples/network: Add testing key/cert to SSL HTTP server example.

This example will now work on all ports with networking and ssl support,
with both axtls and mbedtls.

examples/network/http_server_ssl.py

+import ubinascii as binascii
 try:
     import usocket as socket
 except:
@@ -5,6 +6,35 @@ except:
 import ussl as ssl
 
 
+# This self-signed key/cert pair is randomly generated and to be used for
+# testing/demonstration only.  You should always generate your own key/cert.
+key = binascii.unhexlify(
+    b'3082013b020100024100cc20643fd3d9c21a0acba4f48f61aadd675f52175a9dcf07fbef'
+    b'610a6a6ba14abb891745cd18a1d4c056580d8ff1a639460f867013c8391cdc9f2e573b0f'
+    b'872d0203010001024100bb17a54aeb3dd7ae4edec05e775ca9632cf02d29c2a089b563b0'
+    b'd05cdf95aeca507de674553f28b4eadaca82d5549a86058f9996b07768686a5b02cb240d'
+    b'd9f1022100f4a63f5549e817547dca97b5c658038e8593cb78c5aba3c4642cc4cd031d86'
+    b'8f022100d598d870ffe4a34df8de57047a50b97b71f4d23e323f527837c9edae88c79483'
+    b'02210098560c89a70385c36eb07fd7083235c4c1184e525d838aedf7128958bedfdbb102'
+    b'2051c0dab7057a8176ca966f3feb81123d4974a733df0f958525f547dfd1c271f9022044'
+    b'6c2cafad455a671a8cf398e642e1be3b18a3d3aec2e67a9478f83c964c4f1f')
+cert = binascii.unhexlify(
+    b'308201d53082017f020203e8300d06092a864886f70d01010505003075310b3009060355'
+    b'0406130258583114301206035504080c0b54686550726f76696e63653110300e06035504'
+    b'070c075468654369747931133011060355040a0c0a436f6d70616e7958595a3113301106'
+    b'0355040b0c0a436f6d70616e7958595a3114301206035504030c0b546865486f73744e61'
+    b'6d65301e170d3139313231383033333935355a170d3239313231353033333935355a3075'
+    b'310b30090603550406130258583114301206035504080c0b54686550726f76696e636531'
+    b'10300e06035504070c075468654369747931133011060355040a0c0a436f6d70616e7958'
+    b'595a31133011060355040b0c0a436f6d70616e7958595a3114301206035504030c0b5468'
+    b'65486f73744e616d65305c300d06092a864886f70d0101010500034b003048024100cc20'
+    b'643fd3d9c21a0acba4f48f61aadd675f52175a9dcf07fbef610a6a6ba14abb891745cd18'
+    b'a1d4c056580d8ff1a639460f867013c8391cdc9f2e573b0f872d0203010001300d06092a'
+    b'864886f70d0101050500034100b0513fe2829e9ecbe55b6dd14c0ede7502bde5d46153c8'
+    b'e960ae3ebc247371b525caeb41bbcf34686015a44c50d226e66aef0a97a63874ca5944ef'
+    b'979b57f0b3')
+
+
 CONTENT = b"""\
 HTTP/1.0 200 OK
 
@@ -31,7 +61,8 @@ def main(use_stream=True):
         client_addr = res[1]
         print("Client address:", client_addr)
         print("Client socket:", client_s)
-        client_s = ssl.wrap_socket(client_s, server_side=True)
+        # CPython uses key keyfile/certfile arguments, but MicroPython uses key/cert
+        client_s = ssl.wrap_socket(client_s, server_side=True, key=key, cert=cert)
         print(client_s)
         print("Request:")
         if use_stream: