Code clean-up

[dkarrasch]

This is a companion PR to JuliaLang/julia#46196, in case that one gets accepted. This will fail on nightly before that LinearAlgebra PR gets merged. I have removed the AdjointQ stuff and left the pure code clean-up part. I carefully reviewed which functions are actually overloaded (hence need to be imported) and which ones are only used. I also removed obsolete package specifiers and added a few factorization ldiv!s to make the package proof for some work in LinearAlgebra.jl.

[codecov]

Codecov Report

Base: 85.11% // Head: 84.85% // Decreases project coverage by -0.25% ⚠️

Coverage data is based on head (941f8c0) compared to base (a32eeea).
Patch coverage: 90.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #105      +/-   ##
==========================================
- Coverage   85.11%   84.85%   -0.26%     
==========================================
  Files          10       10              
  Lines        1632     1637       +5     
==========================================
  Hits         1389     1389              
- Misses        243      248       +5     

Impacted Files	Coverage Δ
src/ArrayLayouts.jl	80.72% <ø> (ø)
src/lmul.jl	89.09% <ø> (ø)
src/memorylayout.jl	83.27% <0.00%> (-0.30%)	⬇️
src/mul.jl	82.45% <50.00%> (-1.98%)	⬇️
src/factorizations.jl	89.83% <100.00%> (ø)

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[codecov]

Codecov Report

Base: 85.24% // Head: 85.34% // Increases project coverage by +0.10% 🎉

Coverage data is based on head (56ee510) compared to base (ed0eb07).
Patch coverage: 75.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #105      +/-   ##
==========================================
+ Coverage   85.24%   85.34%   +0.10%     
==========================================
  Files          10       10              
  Lines        1633     1638       +5     
==========================================
+ Hits         1392     1398       +6     
+ Misses        241      240       -1     

Impacted Files	Coverage Δ
src/muladd.jl	74.48% <ø> (ø)
src/memorylayout.jl	84.26% <44.44%> (ø)
src/ldiv.jl	79.24% <67.85%> (+1.79%)	⬆️
src/mul.jl	84.52% <70.00%> (+0.09%)	⬆️
src/ArrayLayouts.jl	80.72% <100.00%> (ø)
src/cumsum.jl	100.00% <100.00%> (ø)
src/factorizations.jl	89.83% <100.00%> (ø)
src/lmul.jl	89.09% <100.00%> (ø)

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