Allow user to create FFT objects using pre-allocated data

[jatinchowdhury18]

No description provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 97.59036% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.56%. Comparing base (4154f22) to head (b60747f).

Files with missing lines	Patch %	Lines
simd/chowdsp_fft_impl_common.hpp	93.54%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #8      +/-   ##
==========================================
+ Coverage   76.38%   76.56%   +0.17%     
==========================================
  Files           5        5              
  Lines        2867     2880      +13     
  Branches      231      221      -10     
==========================================
+ Hits         2190     2205      +15     
+ Misses        677      675       -2     

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