Add metadata decorations to check_x functions in tests

[ktras]

I added empty metadata comments to all of the check_x tests in the test dir in the first commit in this PR. The second commit includes filled in meta data comments that were generated from prompts to Claude using the following type of prompt:

Prompt:

Hello, I want to decorate some code with metadata comments that will be used in a python workflow that does prompt engineering through RAG techniques. Currently the code has the metadata comments but without the fields, "PURPOSE", "KEYWORDS", and "CONTEXT" filled in. Can you use the source code context from this branch of a public github repo, https://github.com/ktras/formal/tree/rag-metadata, to then fill in the "PURPOSE", "KEYWORDS", and "CONTEXT" fields for the following code chunk?

  ! PURPOSE: 
  ! KEYWORDS: 
  ! CONTEXT: 
  function check_2nd_order_laplacian_parabola() result(test_diagnosis)
    type(test_diagnosis_t) test_diagnosis
    procedure(scalar_1D_initializer_i), pointer :: scalar_1D_initializer => parabola
    double precision, parameter :: expected_laplacian = 1D0
#ifdef __GFORTRAN__
    type(laplacian_1D_t) laplacian_scalar
    laplacian_scalar = .laplacian. scalar_1D_t(scalar_1D_initializer, order=2, cells=16, x_min=0D0, x_max=5D0)
#else
    associate(laplacian_scalar => .laplacian. scalar_1D_t(scalar_1D_initializer, order=2, cells=16, x_min=0D0, x_max=5D0))
#endif

      test_diagnosis = passing_test()
      test_diagnosis = test_diagnosis .also. (.all. (laplacian_scalar%values() .approximates. expected_laplacian .within. tight_tolerance)) &
        // " (2nd-order .laplacian. [(x**2)/2]"

#ifndef __GFORTRAN__
    end associate
#endif
  end function
  ! END CODE CHUNK

[rouson]

Suggested change

	! operator-overloading, unit-test, scalar_1D, parabola, 4th-order, structured-grid,
	! defined-operation unit-test, scalar_1D, parabola, 4th-order, structured-grid,

[rouson]

Suggested change

	! unit-test, vector_1D, sinusoid, structured-grid, test-diagnosis, differential-operator,
	! unit-test, vector_1D, sinusoid, structured-grid, staggered-grid, test-diagnosis, differential-operator,

[rouson]

Suggested change

	! structured-grid scalar and vector fields. It constructs two vector_1D_t objects
	! staggered-grid scalar and vector fields. It constructs two vector_1D_t objects

[ktras]

Merging based on verbal approval from @rouson.