SpECTRE Cauchy-characteristic evolution system for rapid, precise waveform extraction

We give full details regarding the new Cauchy-characteristic evolution (CCE) system in SpECTRE. The implementation is built to provide streamlined flexibility for either extracting waveforms during the process of a SpECTRE binary compact object simulation or as a stand-alone module for extracting waveforms from worldtube data provided by another code base. Using our recently presented improved analytic formulation, the CCE system is free of pure-gauge logarithms that would spoil the spectral convergence of the scheme. It gracefully extracts all five Weyl scalars, in addition to the news and the strain. The SpECTRE CCE system makes significant improvements on previous implementations in modularity, ease of use, and speed of computation.