Update references from ITensors to ITensorMPS in documentation and code examples

[VinceNeede]

Description

This mainly updates the docs where ITensors. was still used instead of ITensorMPS.. In the tests and examples ITensors.data has been changed to ITensorMPS.data to improve readability.

Checklist:

• My code follows the style guidelines of this project. Please run using JuliaFormatter; format(".") in the base directory of the repository (~/.julia/dev/ITensorMPS) to format your code according to our style guidelines.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that verify the behavior of the changes I made.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.28%. Comparing base (996375b) to head (393e871).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
ext/ITensorMPSChainRulesCoreExt/abstractmps.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #143      +/-   ##
==========================================
+ Coverage   90.23%   90.28%   +0.05%     
==========================================
  Files          54       54              
  Lines        3583     3583              
==========================================
+ Hits         3233     3235       +2     
+ Misses        350      348       -2     

Flag	Coverage Δ
docs	18.44% <0.00%> (ø)

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[mtfishman]

Very helpful, thanks!