Clean up how we include package data in our distributions (#4755)

* Automatically include package data in distributions

This means that MANIFEST.in and package-data no longer need to be
specified. See https://setuptools.pypa.io/en/latest/userguide/datafiles.html#include-package-data

Author: connorjward

MANIFEST.in

@@ -155,13 +155,13 @@ requires = [
   "mpi4py>3; python_version >= '3.13'",
   "mpi4py; python_version < '3.13'",
   "numpy",
+  # TODO RELEASE
+  # "petsc4py==3.24.0",
   "petsctools",
   "pkgconfig",
   "pybind11",
-  "setuptools>=77.0.3",
-  # TODO RELEASE
-  # "petsc4py==3.24.0",
   "rtree>=1.2",
+  "setuptools>=77.0.3",
 ]
 build-backend = "setuptools.build_meta"
 
@@ -178,6 +178,8 @@ script-files = [
 # Unless specified these files will not be installed along with the
 # rest of the package
 firedrake = [
+  "cython/*.pxi",
+  "cython/*.pyx",
   "evaluate.h",
   "locate.c",
   "icons/*.png",

pyproject.toml

@@ -7,8 +7,8 @@ numpy
 pkgconfig
 petsctools
 pybind11
-setuptools>=77.0.3
 rtree>=1.2
+setuptools>=77.0.3
 
 # Transitive build dependencies
 hatchling