feat: [sc-741] add helper for map with lock

[mr-swifter]

Description

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Fixes Shortcut story [sc-issueNumber]

Squash merging will be used to merge into main (the commit message will be copied from PR text message)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Minimal checklist:

• I have performed a self-review of my own code
• I have added DocC code-level documentation for any public interfaces exported by the package
• I have added unit and/or integration tests that prove my fix is effective or that my feature works

[shortcut-integration]

This pull request has been linked to Shortcut Story #741: Map with lock helper.

[codecov]

Codecov Report

Merging #22 (53ec288) into main (23c503f) will decrease coverage by 4.99%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #22      +/-   ##
==========================================
- Coverage   68.59%   63.59%   -4.99%     
==========================================
  Files           7        8       +1     
  Lines         191      206      +15     
==========================================
  Hits          131      131              
- Misses         60       75      +15     

Impacted Files	Coverage Δ
Sources/ConcurrencyHelpers/MapWithLock.swift	0.00% <0.00%> (ø)

Impacted Files	Coverage Δ
Sources/ConcurrencyHelpers/MapWithLock.swift	0.00% <0.00%> (ø)

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[hassila]

So…. Need to understand the intention - this structure would protect inserts/gets from the dictionary but will not protect the actual values - they are expected to be immutable in the map?