Add Map on itx and deprecate Transform

[apatniv]

Please provide a brief description of the change.

Adds Map Methods to Iterators in itx package, which are more generic versions of Transform methods. Add deprecation warnings to Transform methods.

Which issue does this change relate to?

Address the issue #170

Contribution checklist.

Replace the space in each box with "X" to check it off.

• I have read and understood the CONTRIBUTING guidelines
• All commits in my PR conform to the commit hygiene section
• I have added relevant tests
• I have not added any dependencies

[BooleanCat]

Thanks for the contribution! Could you please rebase this over main and see if the golangci-lint checks pass now.

The README will also need updating to reflect these changes, which either you could do otherwise I can merge without and I'll make the changes myself.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (a8b1349) to head (636d197).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #171   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           34        35    +1     
  Lines          394       397    +3     
=========================================
+ Hits           394       397    +3     

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[apatniv]

@BooleanCat Updated README.md. Let me know if that looks ok.