Add remaining integrated tests to CMake build

[ZedThree]

Plus a few other CMake fixes.

There are a few small non-CMake related changes here that made sense to make in this PR, but they could be pulled out:

• Don't delete test executables before calling make: a small number of tests either call make clean or just rm ./test_name before calling make. This is probably redundant and we don't do it consistently. It also happens to interfere with running make check in CMake builds
• Two small fixes for the PETSc Laplace MAST test: it was always using the same grid file, and it sometimes required one more iteration than the max iterations
• Replace test-datadir with two subtests in test-command-args: this test was essentially just testing the -d command line argument works. test-command-args tests the other arguments, so it makes sense to combine them
• Replace test-fieldgroup with a couple of unit tests. This test tries to check that some expression is ill-formed. This can be replaced with std::is_constructable
• Use the default executable name in test-fieldgroupcomm: very minor change, just for consistency really.

[codecov-io]

Codecov Report

Merging #1833 into next will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##            next   #1833   +/-   ##
=====================================
  Coverage   34.1%   34.1%           
=====================================
  Files        187     187           
  Lines      22689   22689           
=====================================
  Hits        7737    7737           
  Misses     14952   14952

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