R2-solve!-0-allocation

[MohamedLaghdafHABIBOULLAH]

I addressed issue #146 and added a test file to verify zero allocations in solve!.

Additionally, the ShiftedProximalOperators package needs to be updated to the latest version to ensure the tests pass.

@dpo @MaxenceGollier .

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 59.89%. Comparing base (e0f214d) to head (477a490).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
src/R2_alg.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #147      +/-   ##
==========================================
- Coverage   61.53%   59.89%   -1.64%     
==========================================
  Files          11       11              
  Lines        1292     1304      +12     
==========================================
- Hits          795      781      -14     
- Misses        497      523      +26     

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[dpo]

@MohamedLaghdafHABIBOULLAH The allocation tests pass: https://github.com/JuliaSmoothOptimizers/RegularizedOptimization.jl/actions/runs/10715379531/job/29873623718?pr=147#step:6:1292
🎉