Fix point evaluation API change

[leo-collins]

Description

I accidentally changed the API of Function.evaluate in #4543. This changes the shape of the output to how it was before. There were no tests looking for this before so I've added some.

[connorjward]

This is a bug fix (and a critical one at that) so should go into release.

[pbrubeck]

We should also fix calling a Function on a numpy.array

from firedrake import *
mesh = UnitSquareMesh(1, 1)
V = FunctionSpace(mesh, "CG", 1)
u = Function(V)
u(numpy.asarray([0.5, 0.5]))
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[36], line 5
      3 V = FunctionSpace(mesh, "CG", 1)
      4 u = Function(V)
----> 5 u(numpy.asarray([0.5, 0.5]))

File /scratch/brubeckmarti/firedrake-venv/src/ufl/ufl/exproperators.py:345, in _call(self, arg, mapping, component)
    343 def _call(self, arg, mapping=None, component=()):
    344     """Take the restriction or evaluate depending on argument."""
--> 345     if arg in ("+", "-"):
    346         if mapping is not None:
    347             raise ValueError("Not expecting a mapping when taking restriction.")

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

We need something like
345 if isinstance(arg, str) and arg in ("+", "-"):

[pbrubeck]

Ideally we would want Function.__call__ to behave like standard numpy operations if the points are numpy.arrays. This is why I insist that the shape must be preserved. FInAT and FIAT already respect this contract when tabulating finite elements on reference points.

[connorjward]

@leo-collins the recommendations from the meeting yesterday were:

TODO: release - revert to previous behaviour, main - do the sensible thing of allowing a user to pass a single position as a rank-1 vector rather than a rank-2 vector with a length 1 dimension.

I confess I got a bit confused by what we ended up deciding to do but if you agree with that please implement it here and poke me for a review when the tests are passing. I can then make a new release.