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ICU-23364 Implement support for the new CLDR dayOfMonths resource in ICU, along with unit tests. This PR also includes a temporary version of the relevant CLDR data (to be overwritten by the next CLDR integration) and an update to the CLDR-to-ICU tool to account for the new resource.
ICU-22773 Migrate the CLDR conversion tool to Maven
ICU-23333 Create equivalent build.py scripts for all ant tasks
ICU-23475 Update the cldr build.py script to copy the messageFormat tests