function optimizations + new testing framework

[joshuabmoore]

This version brings several major updates to catch22, primarily comprising optimizations to existing code; note that results have been confirmed to be bitwise equivalent with previous versions. There are no major breaking changes for existing users.

The following functions have been optimized (in each case validated against previous implementations on a range of data to confirm bitwise-equivalent results):

• DN_OutlierInclude_p_001_mdrmd
• DN_OutlierInclude_n_001_mdrmd
• PD_PeriodicityWang_th0_01
• FC_LocalSimple_mean1_tauresrat
• SB_TransitionMatrix_3ac_sumdiagcov
• CO_f1ecac
• CO_Embed2_Dist_tau_d_expfit_meandiff
• CO_FirstMin_ac
• SC_FluctAnal_2_rsrangefit_50_1_logi_prop_r1
• SC_FluctAnal_2_dfa_50_1_2_logi_prop_r1
• SP_Summaries_welch_rect_area_5_1
• SP_Summaries_welch_rect_centroid

Changed

• Optimised several C feature implementations without changing their results:
  SC_FluctAnal, PD_PeriodicityWang, FC_LocalSimple, DN_OutlierInclude,
  and the fft routine.
• Reorganised testData/: fixtures moved into testData/basic/ and
  testData/empirical/, and empirical files renamed (e.g. teste1000ts1.txt ->
  e1000_ts0.txt). External scripts referencing the old paths must be updated.

Removed

• Removed the public function DN_OutlierInclude_abs_001 (declaration and
  definition). This was not one of the 22 canonical catch22 features and was
  not used by any language wrapper. Direct callers linking against this symbol
  must migrate.

Fixed

• Corrected the stale include guard name in C/DN_OutlierInclude.h
  (DN_OUTLIERINCLUDE_ABS_001 -> DN_OUTLIERINCLUDE_H).