TensorOperations extension

[lkdvos]

This PR adds support both for using TensorOperations backends within TensorAlgebra methods (i.e. TensorAlgebra.contract(StridedBLAS(), args...), as well as TensorAlgebra backends within TensorOperations (TensorOperations.tensorcontract!(args..., Matricize())).

The end result is that we can now use TensorOperations' machinery to chain together contractions, or simplify the interface when NamedDimArrays or ITensor isn't loaded.
For example, here is a twosite dmrg contraction:

using TensorOperations: @tensor
using TensorAlgebra: Matricize

D1, D2, D3 = 30, 40, 20
d1, d2 = 2, 3
A1 = rand(T, D1, d1, D2) .- 1//2
A2 = rand(T, D2, d2, D3) .- 1//2
rhoL = rand(T, D1, D1) .- 1//2
rhoR = rand(T, D3, D3) .- 1//2
H = rand(T, d1, d2, d1, d2) .- 1//2

@tensor HrA12[a, s1, s2, c] :=
    rhoL[a, a'] * A1[a', t1, b] * A2[b, t2, c'] * rhoR[c', c] * H[s1, s2, t1, t2]
@tensor backend = Matricize() HrA12′[a, s1, s2, c] :=
    rhoL[a, a'] * A1[a', t1, b] * A2[b, t2, c'] * rhoR[c', c] * H[s1, s2, t1, t2]

One interesting thing here is that, similar to #75 , there is not enough information to correctly construct the bipermutation of the output.

Additionally, since this goes both ways I also simplified some of the tests that were verifying results are consistent with TensorOperations, which can now be used through the same interface.

[codecov]

Codecov Report

❌ Patch coverage is 47.05882% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.16%. Comparing base (981f5c0) to head (6c9650d).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
ext/TensorAlgebraTensorOperationsExt.jl	47.05%	18 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
- Coverage   94.39%   91.16%   -3.24%     
==========================================
  Files          14       15       +1     
  Lines         464      498      +34     
==========================================
+ Hits          438      454      +16     
- Misses         26       44      +18     

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[mtfishman]

Looks good, thanks @lkdvos. Maybe we should hold off on merging this until #75 is merged since I think the convention for the destination permutation in contract is changing in that PR.

[lkdvos]

Sounds great, I think the new convention is actually even easier to support so that should be good here