Backport changes to CPU integral code

[awvwgk]

• backport of improved integral evaluation from GPU implementation to CPU implementation
• pass angular momentum to integral evaluator instead of table offset
• some restructuring and cleanup

[codecov]

Codecov Report

Merging #425 (0bc838a) into master (cfc1342) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #425      +/-   ##
==========================================
+ Coverage   40.74%   40.80%   +0.06%     
==========================================
  Files         304      304              
  Lines       50812    50775      -37     
==========================================
+ Hits        20703    20719      +16     
+ Misses      30109    30056      -53     

Impacted Files	Coverage Δ
src/aespot.f90	89.13% <ø> (+8.45%)	⬆️
src/peeq_module.f90	96.54% <ø> (-0.25%)	⬇️
src/scf_module.F90	94.22% <ø> (ø)
src/xtb/hamiltonian.f90	91.80% <ø> (ø)
src/xtb/hamiltonian_gpu.f90	0.00% <ø> (ø)
src/intgrad.f90	52.56% <100.00%> (+3.61%)	⬆️

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