Add data for TensorKit tensor maps

[mtfishman]

Summary

Adds a TensorAlgebra.data method for TensorMap and DiagonalTensorMap in the TensorKit extension, so data and datatype resolve for TensorKit-backed tensors. A TensorMap is not an AbstractArray, so it has no Base.parent(::AbstractArray) self-fallback for the generic data recursion to reach, and the recursion had no leaf to bottom out on. The methods route into the flat block storage vector t.data (type storagetype(t)) and keep recursing through data, so any wrapper on that vector is unwrapped to the true leaf. A lazy AdjointTensorMap already defines Base.parent, so the generic recursion unwraps it with no dedicated method, and a general AbstractTensorMap has no single storage vector, so gets no method.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.14%. Comparing base (727e6d3) to head (c209e04).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #206      +/-   ##
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+ Coverage   81.10%   81.14%   +0.04%     
==========================================
  Files          24       24              
  Lines         905      907       +2     
==========================================
+ Hits          734      736       +2     
  Misses        171      171              

Flag	Coverage Δ
docs	24.25% <0.00%> (-0.06%)	⬇️

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