Refactor of the pixel2map application and add geospatial vector file output (#5606)

* added README.md

* added pixel2map '23 mods

* updated the 2023 code to the current dev branch

* Started the refactoring

* Added app functional test

* updated files for refactoring

* removed call to UserInterface in new cpp code

* refactored started working

* First functional test working

* Removed unused headers

* code reviewed with Kelvin

* fixed Functional Test - started UnitTest

* added the unit test cpp file in the tests folder

* added new test, fixed code in case of 360 crossing

* cleanup for PR

* updated CHANGELOG and docs

* updated institution info

* removed commented-out lines in header

* removed README.md

* pixel2map definition re-inserted into Isis namespace (which was deleted during code cleanup)

* change on testCube path reverted