Make trace() require square matrix independent of layout

[benkay86]

The trace of a matrix can only be computed for square matrices. The implementation of ndarray_linalg::trace::Trace::trace() calls ndarray_linalg::layout::AllocatedArray::square_layout() to verify the matrix is square, but this call also requires the matrix layout to be contiguous. Calling trace on an array view or slice that is not laid out contiguously in memory will generate an ndarray_linalg::error::LinalgError::InvalidStride.

This commit uses ndarray::ArrayBase::is_square() to check that the matrix is square independent of layout.

[codecov]

Codecov Report

Merging #263 (256e5f7) into master (1e4ee3e) will decrease coverage by 0.07%.
The diff coverage is 40.00%.

@@ Coverage Diff @@ ## master #263 +/- ## ========================================== - Coverage 89.10% 89.02% -0.08%  ========================================== Files 71 71 Lines 3578 3582 +4 ========================================== + Hits 3188 3189 +1  - Misses 390 393 +3 

Impacted Files	Coverage Δ
ndarray-linalg/src/trace.rs	57.14% <40.00%> (-42.86%)	⬇️

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[termoshtt]

It makes sense. Thanks!