Safe lax::vec_uninit

[termoshtt]

Split from #333

• Create lax::alloc private submodule
• Remove unsafe marker from lax::vec_uninit

[codecov]

Codecov Report

Merging #334 (802149b) into master (f7356c7) will increase coverage by 0.00%.
The diff coverage is 96.55%.

❗ Current head 802149b differs from pull request most recent head 4737b9c. Consider uploading reports for the commit 4737b9c to get more accurate results

@@           Coverage Diff           @@
##           master     #334   +/-   ##
=======================================
  Coverage   89.92%   89.93%           
=======================================
  Files          72       72           
  Lines        3912     3914    +2     
=======================================
+ Hits         3518     3520    +2     
  Misses        394      394           

Impacted Files	Coverage Δ
lax/src/solveh.rs	75.51% <66.66%> (ø)
lax/src/eigh.rs	95.00% <83.33%> (ø)
lax/src/alloc.rs	90.90% <90.90%> (ø)
lax/src/eig.rs	100.00% <100.00%> (ø)
lax/src/layout.rs	81.15% <100.00%> (ø)
lax/src/least_squares.rs	100.00% <100.00%> (ø)
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 3 more

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