Make planner reusable

[smu160]

• Planner should be re-usable so it can be re-used for FFT's of the same size

• Add regression tests to make sure fft_64/fft_32 gives the same results as fft_64_with_opts_and_plan/fft_32_with_opts_and_plan

@Shnatsel I also added a criterion based benchmark based on these benchmarks. In addition, this new benchmark takes into account that Planner32/Planner64 are now re-usable.

I am thinking we can use criterion's BenchmarkGroup to add rust-fftw3 and RustFFT for comparison. Ideally, this would replace the current benchmarks.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 99.28058% with 1 line in your changes missing coverage. Please review.

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Files	Patch %	Lines
src/twiddles.rs	96.87%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #33 +/- ## ======================================= Coverage ? 99.16% ======================================= Files ? 8 Lines ? 841 Branches ? 0 ======================================= Hits ? 834 Misses ? 7 Partials ? 0 ```

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