feat: add formula shared index

[shcabin]

PR Details

build Shared formula index, optimize performance of GetCellFormula
Related issues: https://github.com/qax-os/excelize/issues/1961

Description

Related Issue

#1961
On my pc, the test mentioned in the issue has been reduced from 27 seconds to 4 seconds

#2030
As discussed in #2030 , the deepcopy will use gitHub/mahae/deepcopy

Motivation and Context

How Has This Been Tested

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.23%. Comparing base (0f19d7f) to head (37ede51).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2118   +/-   ##
=======================================
  Coverage   99.23%   99.23%           
=======================================
  Files          32       32           
  Lines       30176    30205   +29     
=======================================
+ Hits        29945    29974   +29     
  Misses        153      153           
  Partials       78       78           

Flag	Coverage Δ
unittests	99.23% <100.00%> (+<0.01%)	⬆️

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[xuri]

Thanks for your pull request. I've update pull request, fixed code review issues.