Update GitHub Actions to test PostgreSQL 13-17 and remove CircleCI

- Update test matrix to include PostgreSQL 13-17 (supported versions)
- Add beta testing for PostgreSQL 18-beta and 19-beta
- Remove CircleCI configuration after migrating all functionality
- All regression tests preserved from CircleCI implementation

Author: NikolayS

.circleci/config.yml

@@ -139,7 +139,7 @@ jobs:
 
     strategy:
       matrix:
-        postgres-version: ['18-beta']
+        postgres-version: ['18-beta', '19-beta']
       fail-fast: false
 
     services: