revert: Envoy 1.28 upgrade

[LanceEa]

Description

Envoy 1.28 seems to have a regression with the downstream udp/quic listener used for HTTP/3 support. This has been resolved in 1.29 but does not appear to be easily back ported. Therefore, this reverts Envoy 1.28 and go-control-plane update until 1.29 has been released in a few weeks and we can jump to that instead.

Related Issues

https://github.com/envoyproxy/envoy/issues/31036

Testing

No additional testing for revert but we will want to add an http/3 test to our suite so that we can catch this sooner.

Checklist

• [ ] Does my change need to be backported to a previous release?
• [ ] I made sure to update CHANGELOG.md.
• [x] This is unlikely to impact how Ambassador performs at scale.
• [x] My change is adequately tested.
• [ ] I updated DEVELOPING.md with any any special dev tricks I had to use to work on this code efficiently.
• [x] The changes in this PR have been reviewed for security concerns and adherence to security best practices.