Description

This PR merges the phasor_from_signal and phasor_from_signal_fft functions into one:

• Remove phasor_from_signal_fft function.
• Add two parameters to phasor_from_signal: use_fft and rfft (used to be rfft_func). By default, FFT is automatically used when all or at least 8 harmonics are calculated, or a rfft function is specified.
• Change irfft_func parameter to irfft in phasor_to_signal.
• Change Cython implementation to return NaN or Inf instead of 0.0 in case of zero DC.
• Document that zero phasor coordinates are legit and phasor coordinates are undefined for zero DC.
• Update tests.
• Update benchmark tutorial.

The introduction tutorial is currently failing due to #96 and #97

Release note

Summarize the changes in the code block below to be included in the
release notes:

Unify phasor_from_signal functions

Checklist

• The pull request title, summary, and description are concise.
• Related issues are linked in the description.
• New dependencies are explained.
• The source code and documentation can be distributed under the MIT license.
• The source code adheres to code standards.
• New classes, functions, and features are thoroughly tested.
• New, user-facing classes, functions, and features are documented.
• New features are covered in tutorials.
• No files other than source code, documentation, and project settings are added to the repository.