Plans are created lazily on the first FFT_dim call and reused for all
subsequent calls on the same FFT object. PlanCreate<vobj>() can be
called explicitly to pre-warm the cache. PlanDestroy() must be called
before switching to a different vobj type; the destructor cleans up any
live plans automatically.
Update Test_fft.cc and Test_fftf.cc to call PlanDestroy() between the
LatticeComplex and LatticeSpinMatrix sections that reuse the same FFT object.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Peter Boyle
1e29c59bcc