Add support for PostgreSQL 16, drop 11 (#39)

* Add support for PostgreSQL 16

This requires Alpine 3.19

* Drop support for PostgreSQL 11

Version 11 has reached end-of-life (EOL)
https://www.postgresql.org/support/versioning/

* Install aws-cli via apk instead of pip3

This removes python3 and py3-pip as explicit dependencies.
Python is still installed as a derived dependency.

This fixes building on Alpine 3.19

.github/workflows/build-and-push-images.yml

@@ -11,11 +11,11 @@ jobs:
     strategy:
       matrix:
         include:
-          - { postgres: 11, alpine: '3.10' }
           - { postgres: 12, alpine: '3.12' }
           - { postgres: 13, alpine: '3.14' }
           - { postgres: 14, alpine: '3.16' }
           - { postgres: 15, alpine: '3.17' }
+          - { postgres: 16, alpine: '3.19' }
 
     steps:
       - name: Checkout repository