install postgres-16 in CI

[MichelleArk]

Resolves #8286

Problem

We need postgres >= 15 to test dbt-core code that depend on merge operations in dbt-postgres. Specifically this is blocking testing the new microbatch incremental strategy: #10594

Additionally, dbt-postgres is already using postgres 16 in CI so there is some inconsistency there.

Solution

Using: https://computingforgeeks.com/install-and-configure-postgresql-on-ubuntu/

Install postgres 16 onto ubuntu 20.04. We can also consider a service-based approach as what is done in dbt-postgres, but that will likely be a bigger refactor (#10688) + container services are only supported for linux runners. We'd still need to roll our own updates for macos + windows

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.87%. Comparing base (1d3d315) to head (c8ad9ce).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10687      +/-   ##
==========================================
- Coverage   88.92%   88.87%   -0.05%     
==========================================
  Files         180      180              
  Lines       22785    22785              
==========================================
- Hits        20261    20250      -11     
- Misses       2524     2535      +11     

Flag	Coverage Δ
integration	86.10% <ø> (-0.14%)	⬇️
unit	62.36% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Unit Tests	62.36% <ø> (ø)
Integration Tests	86.10% <ø> (-0.14%)	⬇️

[MichelleArk]

Going to merge this as-is for now, with some follow-up ideas to speed up windows runs:

• create a separate image for windows that pre-installs postgres16
• uninstall existing postgres package, use choco install (which appears to be faster), and then figure out how to start postgres as a (or start postgres up on on our own)
  • uninstall guide: https://stackoverflow.com/questions/113542/how-can-i-uninstall-an-application-using-powershell
  • starting the service will likely take a good amount of time to figure out
  • can take inspiration from https://github.com/ikalnytskyi/action-setup-postgres/blob/master/action.yml, or try to use the action directly (first unsuccessful attempt here: use ikalnytskyi/action-setup-postgres@v6 #10689)

Issue here: #10696