ci: optimize integration tests with shared compile step (#477)

Reduces test time >50%.

Added a step to compile all test files and run tests based on the name.
Also separated all tests to it's own package.

.golangci.yaml

@@ -30,21 +30,3 @@ linters-settings:
         replacement: 'a[b:]'
 issues:
   fix: true
-run:
-  build-tags:
-    - integration
-    - cloudsqlpg
-    - postgres
-    - alloydb
-    - spanner
-    - cloudsqlmssql
-    - cloudsqlmysql
-    - neo4j
-    - dgraph
-    - mssql
-    - mysql
-    - http
-    - alloydb_ai_nl
-    - bigtable
-    - bigquery
-    - sqlite