[ITensorMPS] Allow customizing apply

[mtfishman]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 44.03%. Comparing base (23723c7) to head (e096763).
Report is 1 commits behind head on main.

❗ Current head e096763 differs from pull request most recent head f5cdd6e. Consider uploading reports for the commit f5cdd6e to get more accurate results

Files	Patch %	Lines
src/lib/ITensorMPS/src/mpo.jl	0.00%	4 Missing ⚠️
src/lib/ITensorMPS/test/base/test_mps.jl	0.00%	2 Missing ⚠️
...MPS/ext/ITensorMPSChainRulesCoreExt/abstractmps.jl	0.00%	1 Missing ⚠️
src/lib/ITensorMPS/test/base/test_fermions.jl	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1440       +/-   ##
===========================================
- Coverage   59.53%   44.03%   -15.50%     
===========================================
  Files         139      143        +4     
  Lines        9005     9370      +365     
===========================================
- Hits         5361     4126     -1235     
- Misses       3644     5244     +1600     

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