Homelessness has shot up in California and elsewhere on the West Coast over the past two years, a federal report said Wednesday, as rising rents and other housing pressures forced more people from the margins onto the street. California’s homeless population went up 14 percent, to 134,278 — the most by far of any state, and representing 31 percent of all the homeless people in the U.S., according to the federal Department of Housing and Urban Development.