icu4c: add full support for Asturian through es-rXA

Change-Id: I48b892759e024700ce3a23d4ee1ee4104ee5b1b1
common: ucnv: add in _50 symbols

-needed for Nvidia (T4) audio (nvoice)

Change-Id: If12ce0c26ed3530bbefa1c69f0565b1b8eea99b5