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.

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• 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