NEW YORK — Mayor Eric Adams called off a plan Wednesday to cut all city agency budgets by 5% this spring — but also announced he’s going to slash nearly $600 million in projected spending on housing and services for newly arrived migrants. Under a plan first rolled out by City Hall in fall 2023, all agencies were supposed to face 5% budget reductions in April — on top of two previous rounds of 5% cuts in November and January — in order to offset costs associated with caring for the migrants. But in a statement Wednesday afternoon, the mayor said he’s canceling the April cuts thanks to “better-…