feat(spanner/spansql): add support for foreign key actions

[toga4]

This PR adds support for foreign key actions

CREATE TABLE ShoppingCarts (
  CartId INT64 NOT NULL,
  CustomerId INT64 NOT NULL,
  CustomerName STRING(MAX) NOT NULL,
  CONSTRAINT FKShoppingCartsCustomers FOREIGN KEY(CustomerId, CustomerName)
    REFERENCES Customers(CustomerId, CustomerName) ON DELETE CASCADE,
) PRIMARY KEY(CartId);

ALTER TABLE ShoppingCarts ADD CONSTRAINT FKShoppingCartsCustomers FOREIGN KEY(CustomerId, CustomerName)
    REFERENCES Customers(CustomerId, CustomerName) ON DELETE NO ACTION,