feat: #993 added ipr_tensor

[zerothi]

Added the ipr_tensor method for extracting IPR in a tensor product.

• Closes Tensor-generalization of IPR #993
• Added tests for new/changed functions?
• Documentation for functionality in docs/
• Changes documented in changes/<num>.<type>.rst

[codecov]

Codecov Report

❌ Patch coverage is 96.87500% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 86.64%. Comparing base (2f5fe2a) to head (e4839f0).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/sisl/physics/state.py	93.33%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #994   +/-   ##
=======================================
  Coverage   86.63%   86.64%           
=======================================
  Files         414      414           
  Lines       54709    54741   +32     
=======================================
+ Hits        47399    47430   +31     
- Misses       7310     7311    +1     

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