feat: add backend logic for determining tasks tab visibility (#18401)

This PR implements the backend logic for determining if the Tasks tab
should be visible in the web UI as described in [the
RFC](https://www.notion.so/coderhq/Coder-Tasks-207d579be5928053ab68c8d9a4b59eaa?source=copy_link#210d579be5928013ab5acbe69a2f548b).

The frontend component will be added in a follow-up PR once the entire
Tasks backend is implemented so as not to break the dogfood environment
until then.

coderd/database/dbauthz/dbauthz.go

@@ -3451,6 +3451,11 @@ func (q *querier) GetWorkspacesEligibleForTransition(ctx context.Context, now ti
 	return q.db.GetWorkspacesEligibleForTransition(ctx, now)
 }
 
+func (q *querier) HasTemplateVersionsWithAITask(ctx context.Context) (bool, error) {
+	// Anyone can call HasTemplateVersionsWithAITask.
+	return q.db.HasTemplateVersionsWithAITask(ctx)
+}
+
 func (q *querier) InsertAPIKey(ctx context.Context, arg database.InsertAPIKeyParams) (database.APIKey, error) {
 	return insert(q.log, q.auth,
 		rbac.ResourceApiKey.WithOwner(arg.UserID.String()),

coderd/database/dbauthz/dbauthz_test.go

@@ -4566,6 +4566,9 @@ func (s *MethodTestSuite) TestSystemFunctions() {
 	s.Run("GetProvisionerJobByIDForUpdate", s.Subtest(func(db database.Store, check *expects) {
 		check.Args(uuid.New()).Asserts(rbac.ResourceProvisionerJobs, policy.ActionRead).Errors(sql.ErrNoRows)
 	}))
+	s.Run("HasTemplateVersionsWithAITask", s.Subtest(func(db database.Store, check *expects) {
+		check.Args().Asserts()
+	}))
 }
 
 func (s *MethodTestSuite) TestNotifications() {