Governor Deval Patrick detailed a plan Tuesday to produce 10,000 multifamily housing units a year through 2020 in an effort to keep young professionals from leaving Massachusetts. The initiative includes a program called Compact Neighborhoods that will encourage and create housing near workplaces, public transportation, and city and village centers, Patrick said. The plan is meant to complement other state initiatives that promote so-called smart-growth — the creation of housing near train stations and urban centers, state officials said. It would more than double the amount of housing with five or more units — including apartments and condominiums — expected to be built by the end of this year, the state said. The move comes amid a growing chorus of housing specialists who are stressing the importance of building more higher-density housing.