Upgrade Postgres v14 --> v16 or v17

[spwoodcock]

Is your feature request related to a problem? Please describe.

• Postgres 14 is 3yrs out of date at this point.
• Keeping on top of latest releases eases the maintenance burden / upgrade path going forward.

Describe the solution you'd like

• [ ] Add a migration for v14 --> v16 if required.
• [ ] Update all docker compose files references to POSTGIS_IMG_TAG.
• [ ] Update Github env vars.

[spwoodcock]

Work done on drone-tm already using pgautoupgrade.

Guide:

https://github.com/pgautoupgrade/docker-pgautoupgrade/wiki/Automating-The-Upgrade