SQLStore: Ensure that sessions are always closed (#55864)

* SQLStore: Ensure that sessions are always closed

Delete `NewSession()` in favour of `WithDbSession()`

* Add WithDbSessionForceNewSession to the interface

* Apply suggestions from code review

pkg/services/sqlstore/mockstore/mockstore.go

@@ -222,6 +222,10 @@ func (m *SQLStoreMock) WithDbSession(ctx context.Context, callback sqlstore.DBTr
 	return m.ExpectedError
 }
 
+func (m *SQLStoreMock) WithNewDbSession(ctx context.Context, callback sqlstore.DBTransactionFunc) error {
+	return m.ExpectedError
+}
+
 func (m *SQLStoreMock) GetOrgQuotaByTarget(ctx context.Context, query *models.GetOrgQuotaByTargetQuery) error {
 	return m.ExpectedError
 }