Update postgres Docker tag to v16

[smorimoto]

No description provided.

[smorimoto]

The release of Timescale for pg16 is not yet available in the upstream repository. Keep another PR open.

[smorimoto]

@lubien Could you review this and #215?

[davissp14]

I'll do my best to take a look at it this week. I apologize for the delay on this.

[smorimoto]

Thanks a lot 🙃

[smorimoto]

@davissp14 Could you check this?

[smorimoto]

Rebased to latest master.

[davissp14]

@smorimoto Were you able to test this?

I ran into a few issues when trying to run PG 16 with repmgr.

1. Repmgr 5.4.1 is required for PG 16. You can install an earlier version of repmgr, but the binaries end up injected into the wrong path.
2. Repmgr 5.4.1 requires libc > 2.38 and there doesn't seem to be a stable debian package for this.

My initial thought was to use ubuntu for the base image, but this would likely lead to more collation issues for existing users since we use the same Dockerfile for all versions.

[davissp14]

Closing in favor of: #233