Test Python bounds only

This bumps the newest python version tested to 3.11 and drops testing
for 3.7, 3.8, and 3.9. We only test the lower and upper python version
bounds.

We switch to an ed25519 ssh key instead of rsa because Ubuntu Jammy
defaults to rsa + sha2 and Gerrit 3.4.4 does not understand this. This
results in a golden site version bump.

Change-Id: I3989460575fa9c389233244683318a6cfded68fe

.zuul.yaml

@@ -9,12 +9,8 @@
         - nox-linters
         - nox-py36:
             nodeset: ubuntu-bionic
-        - nox-py37:
-            nodeset: ubuntu-bionic
-        - nox-py38:
-            nodeset: ubuntu-focal
-        - nox-py39:
-            nodeset: ubuntu-focal
+        - nox-py311:
+            nodeset: ubuntu-jammy
     gate:
       jobs: *jobs
     promote:

git_review/tests/__init__.py

@@ -40,7 +40,7 @@ else:
 WAR_URL = 'https://gerrit-releases.storage.googleapis.com/gerrit-3.4.4.war'
 # Update GOLDEN_SITE_VER for every change altering golden site, including
 # WAR_URL changes. Set new value to something unique (just +1 it for example)
-GOLDEN_SITE_VER = '6'
+GOLDEN_SITE_VER = '7'
 
 
 # NOTE(yorik-sar): This function needs to be a perfect hash function for
@@ -164,8 +164,9 @@ class GerritHelpers(DirHelpers):
         with open(golden_ver_file, 'w') as f:
             f.write(GOLDEN_SITE_VER)
 
-        # create SSH public key
-        utils.run_cmd('ssh-keygen', '-t', 'rsa', '-b', '4096', '-m', 'PEM',
+        # Create SSH public key. This is not RSA because Jammy wants to
+        # do rsa + sha2 by default and Gerrit 3.4.4 does not understand this.
+        utils.run_cmd('ssh-keygen', '-t', 'ed25519',
                       '-f', self._dir('gsite', 'test_ssh_key'), '-N', '')
 
     def _run_gerrit_cli(self, command, *args):