Centralize Postgres test fixture in internal/test

Each package that exercises the database against a real Postgres
carried its own copy of the connection bootstrap and schema setup.
Those copies had already drifted: some keyed off PROBO_TEST_PG_ADDR
with hardcoded defaults, others off PROBO_TEST_PG_URL, and the
agentrun/coredata suites hand-applied individual agent_runs
migrations to ensure the table existed.

Introduce a single test.PGClient helper that parses PROBO_TEST_PG_URL
(falling back to the local compose database), runs the full coredata
migration set once per process, and skips when no database is
reachable so make test stays a pure unit-test run. Migrate the
agentrun, coredata, cookiebanner, iam, and thirdparty suites onto it
and delete the duplicated helpers so the bootstrap can no longer
diverge.

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/agentrun/service_test.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"go.probo.inc/probo/internal/test"
 	"go.probo.inc/probo/pkg/agentrun"
 	"go.probo.inc/probo/pkg/coredata"
 	"go.probo.inc/probo/pkg/gid"
@@ -27,7 +28,7 @@ import (
 )
 
 func TestService_Get(t *testing.T) {
-	client := pgClient(t)
+	client := test.PGClient(t)
 	svc := agentrun.NewService(client)
 
 	run := insertPendingRun(
@@ -49,7 +50,7 @@ func TestService_Get(t *testing.T) {
 }
 
 func TestService_ListForOrganizationID(t *testing.T) {
-	client := pgClient(t)
+	client := test.PGClient(t)
 	svc := agentrun.NewService(client)
 
 	orgID := insertTestOrganization(t, client)
@@ -81,7 +82,7 @@ func TestService_ListForOrganizationID(t *testing.T) {
 }
 
 func TestService_CountForOrganizationID(t *testing.T) {
-	client := pgClient(t)
+	client := test.PGClient(t)
 	svc := agentrun.NewService(client)
 
 	orgID := insertTestOrganization(t, client)