Use lapack-sys crate directly from lax crate

[termoshtt]

First step of #327.

The problem of lapack crate is it requires slice &[T] which must be initialized while the pointer-based API in lapack-sys does not.

[codecov]

Codecov Report

Merging #328 (2fc0ac8) into master (0cfde73) will increase coverage by 0.15%.
The diff coverage is 96.74%.

@@            Coverage Diff             @@
##           master     #328      +/-   ##
==========================================
+ Coverage   89.90%   90.06%   +0.15%     
==========================================
  Files          71       71              
  Lines        3756     3864     +108     
==========================================
+ Hits         3377     3480     +103     
- Misses        379      384       +5     

Impacted Files	Coverage Δ
lax/src/solveh.rs	75.00% <72.00%> (-3.79%)	⬇️
lax/src/eigh.rs	94.82% <91.17%> (+0.59%)	⬆️
lax/src/cholesky.rs	100.00% <100.00%> (ø)
lax/src/eig.rs	100.00% <100.00%> (ø)
lax/src/least_squares.rs	100.00% <100.00%> (ø)
lax/src/lib.rs	96.55% <100.00%> (+4.24%)	⬆️
lax/src/opnorm.rs	100.00% <100.00%> (ø)
lax/src/qr.rs	100.00% <100.00%> (ø)
lax/src/rcond.rs	100.00% <100.00%> (ø)
lax/src/solve.rs	100.00% <100.00%> (ø)
... and 4 more

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