No workvec in rotate, foreach in fft_conv

[ZongyuLi-umich]

clean up commits

[codecov]

Codecov Report

Merging #19 (d46c881) into main (1bbb40b) will decrease coverage by 0.26%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #19      +/-   ##
==========================================
- Coverage   98.83%   98.57%   -0.27%     
==========================================
  Files           8        8              
  Lines         600      630      +30     
==========================================
+ Hits          593      621      +28     
- Misses          7        9       +2     

Impacted Files	Coverage Δ
src/fft_convolve.jl	100.00% <100.00%> (ø)
src/plan-psf.jl	100.00% <100.00%> (ø)
src/plan-rotate.jl	100.00% <100.00%> (ø)
src/rotatez.jl	99.02% <100.00%> (-0.98%)	⬇️

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[ZongyuLi-umich]

@JeffFessler, I implemeted foreach version of fft_convolve.
Then I rewrote project.jl and backproject.jl with integration of foreach version of imrotate and fft_convolve,
however, I found this is even slower than the :mem version, see the statistics below.
I didn't upload my projection code to github, because I think you might want to change my fft_conv first.

one, fast
337.220 ms
one, mem
793.918 ms
one, foreach
815.774 ms
two, fast
266.518 ms
two, mem
618.369 ms
two, foreach
734.362 ms

[JeffFessler]

Ok, I have merged this for now and I will study the timings over the weekend.