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