Use LowRankMatrices instead of LowRankApprox

[jishnub]

This improves the package load time.
On master

julia> @time using ApproxFunBase
  8.988063 seconds (19.69 M allocations: 1.440 GiB, 3.62% gc time, 0.46% compilation time: 58% of which was recompilation)

This PR

julia> @time using ApproxFunBase
  7.450542 seconds (13.31 M allocations: 1.160 GiB, 3.67% gc time, 0.55% compilation time: 58% of which was recompilation)

These timings are on Julia v1.9.2

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -7.59% ⚠️

Comparison is base (4f33475) 71.88% compared to head (136283b) 64.29%.
Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #511      +/-   ##
==========================================
- Coverage   71.88%   64.29%   -7.59%     
==========================================
  Files          81       81              
  Lines        8546     8565      +19     
==========================================
- Hits         6143     5507     -636     
- Misses       2403     3058     +655     

Files Changed	Coverage Δ
src/ApproxFunBase.jl	72.00% <ø> (-12.00%)	⬇️
src/Operators/general/InterlaceOperator.jl	76.00% <ø> (-5.34%)	⬇️
src/Fun.jl	62.37% <100.00%> (-5.43%)	⬇️
src/LinearAlgebra/helper.jl	69.64% <100.00%> (+0.71%)	⬆️
src/Operators/banded/Conversion.jl	87.09% <100.00%> (+0.65%)	⬆️
src/eigen.jl	90.47% <100.00%> (-5.96%)	⬇️

... and 43 files with indirect coverage changes

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