Fix type issues

[lostella]

This fixes some type issues spotted with the aid of JET.jl (I hope I interpreted the complaints right).

This should bring some performance improvement in iterative cases where CG is used to compute prox.

[codecov]

Codecov Report

Merging #141 (838d991) into master (04204f7) will decrease coverage by 0.07%.
The diff coverage is 95.23%.

@@            Coverage Diff             @@
##           master     #141      +/-   ##
==========================================
- Coverage   95.88%   95.80%   -0.08%     
==========================================
  Files          79       79              
  Lines        2382     2386       +4     
==========================================
+ Hits         2284     2286       +2     
- Misses         98      100       +2     

Impacted Files	Coverage Δ
src/functions/indGraphSkinny.jl	100.00% <ø> (ø)
src/functions/leastSquaresDirect.jl	93.42% <0.00%> (ø)
src/calculus/tilt.jl	100.00% <100.00%> (ø)
src/functions/indPSD.jl	100.00% <100.00%> (ø)
src/functions/leastSquaresIterative.jl	97.77% <100.00%> (ø)
src/utilities/linops.jl	68.08% <100.00%> (-1.69%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 04204f7...838d991. Read the comment docs.

[lostella]

This should bring some performance improvement in iterative cases where CG is used to compute prox.

Indeed:

  ["LeastSquares", ("ComplexF64", "(11, 5)", 0, 1)] 0.93 (5%) ✅  0.95 (1%) ✅
  ["LeastSquares", ("ComplexF64", "(11, 5)", 1, 1)] 0.93 (5%) ✅  0.87 (1%) ✅
  ["LeastSquares", ("ComplexF64", "(5, 11)", 0, 1)]   0.95 (5%)  0.96 (1%) ✅
  ["LeastSquares", ("ComplexF64", "(5, 11)", 1, 1)] 0.94 (5%) ✅  0.87 (1%) ✅
     ["LeastSquares", ("Float64", "(11, 5)", 0, 1)] 0.92 (5%) ✅  0.96 (1%) ✅
     ["LeastSquares", ("Float64", "(11, 5)", 1, 1)] 0.93 (5%) ✅  0.87 (1%) ✅
     ["LeastSquares", ("Float64", "(5, 11)", 0, 1)] 0.94 (5%) ✅  0.97 (1%) ✅
     ["LeastSquares", ("Float64", "(5, 11)", 1, 1)] 0.94 (5%) ✅  0.87 (1%) ✅