Allow multiple subdomain data

[jpdean]

Currently, UFL checks that all integrals of a particular type in a form have the same subdomain data (using the UFL ID). I'm not sure this should be UFL's job. Instead, UFL should probably just collect the data into a list and let the finite element library (e.g. dolfinx) either check the data is the same or make use of the additional data. This PR addresses this.

This PR requires https://github.com/FEniCS/dolfinx/pull/2369