Introduce droptzeros! and apply it at the end of + methods

[albertomercurio]

This allows to have C = A - A with zero elements, as expected.

[codecov]

Codecov Report

❌ Patch coverage is 73.14815% with 58 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.16%. Comparing base (7f68c3c) to head (254dd23).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/matrix_coo/matrix_coo.jl	66.12%	21 Missing ⚠️
src/matrix_csc/matrix_csc.jl	73.58%	14 Missing ⚠️
src/matrix_csr/matrix_csr.jl	73.58%	14 Missing ⚠️
src/matrix_csc/matrix_csc_kernels.jl	76.47%	4 Missing ⚠️
src/matrix_csr/matrix_csr_kernels.jl	76.47%	4 Missing ⚠️
src/core.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #42      +/-   ##
==========================================
- Coverage   89.13%   87.16%   -1.98%     
==========================================
  Files          18       18              
  Lines        1556     1768     +212     
==========================================
+ Hits         1387     1541     +154     
- Misses        169      227      +58     

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[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Benchmark Results'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.30.

Benchmark suite	Current: 254dd23	Previous: 7f68c3c	Ratio
Matrix-Vector Multiplication/Array/CSC	6318927 ns	3646599 ns	1.73
Matrix-Vector Multiplication/Array/COO	7842197 ns	5304178.5 ns	1.48
Matrix-Vector Multiplication/Array/CSR	566052.5 ns	426714 ns	1.33
Sparse Vector/Array/Sum	18.665330661322646 ns	12.769539078156313 ns	1.46
Sparse Vector/Array/Sparse-Dense dot	137.61822376009226 ns	104.8817891373802 ns	1.31
Format Conversions/Array/CSC → COO	6758512.5 ns	3185176 ns	2.12
Format Conversions/Array/COO → CSC	17189868 ns	10625875 ns	1.62
Format Conversions/Array/CSR → COO	6799125.5 ns	3117591 ns	2.18
Format Conversions/Array/COO → CSR	65924321.5 ns	50542705.5 ns	1.30
Sparse + Dense Addition/Array/CSC	394342434 ns	112358841 ns	3.51
Sparse + Dense Addition/Array/COO	394539974 ns	119452873.5 ns	3.30
Sparse + Dense Addition/Array/CSR	392690018 ns	116325260 ns	3.38
Sparse + Dense Addition/JLArray/CSC	677110757 ns	386240178 ns	1.75
Sparse + Dense Addition/JLArray/COO	730519622 ns	436123254.5 ns	1.68
Sparse + Dense Addition/JLArray/CSR	704628923.5 ns	417915009 ns	1.69
Kronecker Product/Array/COO	151771.5 ns	61705 ns	2.46
Matrix-Matrix Multiplication/Array/CSC	510319259 ns	276582326 ns	1.85
Matrix-Matrix Multiplication/Array/COO	548974093.5 ns	253868127.5 ns	2.16
Matrix-Matrix Multiplication/Array/CSR	105883940 ns	48808790.5 ns	2.17
Matrix-Matrix Multiplication/JLArray/COO	24445287897 ns	18353681047 ns	1.33
Sparse + Sparse Addition/Array/CSC	31148099 ns	12234182 ns	2.55
Sparse + Sparse Addition/Array/COO	115206926 ns	85729431 ns	1.34
Sparse + Sparse Addition/Array/CSR	30927558 ns	11886900.5 ns	2.60
Sparse + Sparse Addition/JLArray/CSC	1275056378.5 ns	595895985 ns	2.14
Sparse + Sparse Addition/JLArray/CSR	1241543634 ns	592865805 ns	2.09
Three-argument dot/Array/CSC	593236 ns	447492 ns	1.33

This comment was automatically generated by workflow using github-action-benchmark.