Adds test for a full P2Function to FunctionIteratorTest.

Test currently fails because we get DoFs that claim to be neither
on an edge nor at a vertex.
23 jobs for kohl-mohr/FunctionIteratorP2 in 16 minutes and 50 seconds (queued for 2 seconds)
latest
Name Stage Failure
failed
clang_10.0_eigen_petsc Pretest

Total Test time (real) = 402.25 sec

The following tests FAILED:
185 - FunctionIteratorTest1 (Failed)
186 - FunctionIteratorTest2 (Failed)
187 - FunctionIteratorTest8 (Failed)
Errors while running CTest
ERROR: Job failed: exit code 1
failed
gcc_10_mpionly_dbg Pretest

Total Test time (real) = 441.28 sec

The following tests FAILED:
144 - FunctionIteratorTest1 (Failed)
145 - FunctionIteratorTest2 (Failed)
146 - FunctionIteratorTest8 (Failed)
Errors while running CTest
ERROR: Job failed: exit code 1