Add LuTridiagonalWork, merge Tridiagonal_ into Lapack

[termoshtt]

For #168

[codecov]

Codecov Report

Merging #349 (4913818) into master (ad19250) will increase coverage by 0.07%.
The diff coverage is 85.07%.

@@            Coverage Diff             @@
##           master     #349      +/-   ##
==========================================
+ Coverage   90.04%   90.11%   +0.07%     
==========================================
  Files          74       77       +3     
  Lines        4580     4613      +33     
==========================================
+ Hits         4124     4157      +33     
  Misses        456      456              

Impacted Files	Coverage Δ
lax/src/tridiagonal/matrix.rs	35.71% <35.71%> (ø)
lax/src/tridiagonal/solve.rs	95.65% <95.65%> (ø)
lax/src/tridiagonal/lu.rs	96.87% <96.87%> (ø)
lax/src/lib.rs	95.83% <100.00%> (+0.52%)	⬆️
lax/src/tridiagonal/rcond.rs	100.00% <100.00%> (ø)

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more