feat(tls): remove commonName in certificate generation

[mmorel-35]

Checklist prior to review

• Link to relevant issue as well as docs and UI issues -- closes deprecating the use of commonName in certificate generation #6625
• This will not break child repos: it doesn't hardcode values (.e.g "kumahq" as a image registry) and it will work on Windows, system specific functions like syscall.Mkfifo have equivalent implementation on the other OS --
• Tests (Unit test, E2E tests, manual test on universal and k8s) --
• Do you need to update UPGRADE.md? --
• Does it need to be backported according to the backporting policy? --
• Do you need to explicitly set a > Changelog: entry here or add a ci/ label to run fewer/more tests?

[lobkovilya]

Probably we have to outline the places affected by this change:

• kumactl generate tls-certificate generates certificates without CN
• autogenerated TLS certificate for kuma-cp (when general.tlsCertFile is not provided) won't have CN

But I'm not sure if this should be mentioned in UPGRADE.md or just CHANGELOG is enough. @bartsmykla @michaelbeaumont what do you think?

[michaelbeaumont]

I think a mention in UPGRADE.md is appropriate, we just mention that this only affects you if you explicitly rely on the common name being present in generated certs.

[michaelbeaumont]

LGTM