Benchmark more FFT implementations

[astral4]

As of right now, there are three crates being benchmarked: fftw, phastft, and rustfft. We should add benchmarks for other Rust implementations and bindings.

A non-exhaustive list:

• chfft (specifically chfft::CFft1D)
• fourier
• arrayfire (specifically arrayfire::fft_inplace and arrayfire::ifft_inplace)
• GSL (specifically rgsl::fft::radix2)

Presenting results in Markdown table format will become unwieldy, so we should eventually switch to generating charts.