Tweak cipher selection to make TLS < 1.2 work with OpenSSL 3.

Taken from Debian:

  https://salsa.debian.org/python-team/packages/mercurial/-/blob/debian/master/debian/patches/openssl_3_cipher_tlsv1.patch

--- a/mercurial/sslutil.py
+++ b/mercurial/sslutil.py
@@ -117,17 +117,17 @@ def _hostsettings(ui, hostname):
     ciphers = ui.config(b'hostsecurity', b'%s:ciphers' % bhostname, ciphers)
 
     # If --insecure is used, we allow the use of TLS 1.0 despite config options.
     # We always print a "connection security to %s is disabled..." message when
     # --insecure is used. So no need to print anything more here.
     if ui.insecureconnections:
         minimumprotocol = b'tls1.0'
         if not ciphers:
-            ciphers = b'DEFAULT'
+            ciphers = b'DEFAULT:@SECLEVEL=0'
 
     s[b'minimumprotocol'] = minimumprotocol
     s[b'ciphers'] = ciphers
 
     # Look for fingerprints in [hostsecurity] section. Value is a list
     # of <alg>:<fingerprint> strings.
     fingerprints = ui.configlist(
         b'hostsecurity', b'%s:fingerprints' % bhostname
@@ -621,17 +621,17 @@ def wrapserversocket(
 
     # Improve forward secrecy.
     sslcontext.options |= getattr(ssl, 'OP_SINGLE_DH_USE', 0)
     sslcontext.options |= getattr(ssl, 'OP_SINGLE_ECDH_USE', 0)
 
     # In tests, allow insecure ciphers
     # Otherwise, use the list of more secure ciphers if found in the ssl module.
     if exactprotocol:
-        sslcontext.set_ciphers('DEFAULT')
+        sslcontext.set_ciphers('DEFAULT:@SECLEVEL=0')
     elif util.safehasattr(ssl, b'_RESTRICTED_SERVER_CIPHERS'):
         sslcontext.options |= getattr(ssl, 'OP_CIPHER_SERVER_PREFERENCE', 0)
         # pytype: disable=module-attr
         sslcontext.set_ciphers(ssl._RESTRICTED_SERVER_CIPHERS)
         # pytype: enable=module-attr
 
     if requireclientcert:
         sslcontext.verify_mode = ssl.CERT_REQUIRED
--- a/tests/test-https.t
+++ b/tests/test-https.t
@@ -356,19 +356,19 @@ Start servers running supported TLS vers
   $ cat ../hg1.pid >> $DAEMON_PIDS
   $ hg serve -p $HGPORT2 -d --pid-file=../hg2.pid --certificate=$PRIV \
   > --config devel.serverexactprotocol=tls1.2
   $ cat ../hg2.pid >> $DAEMON_PIDS
   $ cd ..
 
 Clients talking same TLS versions work
 
-  $ P="$CERTSDIR" hg --config hostsecurity.minimumprotocol=tls1.0 --config hostsecurity.ciphers=DEFAULT id https://localhost:$HGPORT/
+  $ P="$CERTSDIR" hg --config hostsecurity.minimumprotocol=tls1.0 --config hostsecurity.ciphers=DEFAULT:@SECLEVEL=0 id https://localhost:$HGPORT/
   5fed3813f7f5
-  $ P="$CERTSDIR" hg --config hostsecurity.minimumprotocol=tls1.1 --config hostsecurity.ciphers=DEFAULT id https://localhost:$HGPORT1/
+  $ P="$CERTSDIR" hg --config hostsecurity.minimumprotocol=tls1.1 --config hostsecurity.ciphers=DEFAULT:@SECLEVEL=0 id https://localhost:$HGPORT1/
   5fed3813f7f5
   $ P="$CERTSDIR" hg --config hostsecurity.minimumprotocol=tls1.2 id https://localhost:$HGPORT2/
   5fed3813f7f5
 
 Clients requiring newer TLS version than what server supports fail
 
   $ P="$CERTSDIR" hg id https://localhost:$HGPORT/
   (could not negotiate a common security protocol (tls1.1+) with localhost; the likely cause is Mercurial is configured to be more secure than the server can support)
@@ -400,17 +400,17 @@ Clients requiring newer TLS version than
 
   $ hg --config hostsecurity.minimumprotocol=tls1.2 id --insecure https://localhost:$HGPORT1/
   warning: connection security to localhost is disabled per current settings; communication is susceptible to eavesdropping and tampering
   5fed3813f7f5
 
 The per-host config option overrides the default
 
   $ P="$CERTSDIR" hg id https://localhost:$HGPORT/ \
-  > --config hostsecurity.ciphers=DEFAULT \
+  > --config hostsecurity.ciphers=DEFAULT:@SECLEVEL=0 \
   > --config hostsecurity.minimumprotocol=tls1.2 \
   > --config hostsecurity.localhost:minimumprotocol=tls1.0
   5fed3813f7f5
 
 The per-host config option by itself works
 
   $ P="$CERTSDIR" hg id https://localhost:$HGPORT/ \
   > --config hostsecurity.localhost:minimumprotocol=tls1.2