added CUDA support for local extrema

[hzarei4]

Hello,

This PR adds CUDA support for local extrema on CuArrays through /ext/CUDASupportExt.jl.

It implements findlocalextrema for CUDA arrays, which in turn enables findlocalmaxima and findlocalminima with behavior aligned with the existing ImageFiltering.jl API. I also added CUDA tests based on the existing CPU extrema tests.

I hope this is helpful. Please let me know if anything should be corrected or improved.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 91 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.42%. Comparing base (d3c2202) to head (8ebbd40).

Files with missing lines	Patch %	Lines
ext/CUDASupportExt.jl	0.00%	91 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #291      +/-   ##
==========================================
- Coverage   91.56%   86.42%   -5.15%     
==========================================
  Files          12       13       +1     
  Lines        1672     1672              
==========================================
- Hits         1531     1445      -86     
- Misses        141      227      +86     

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