BOSTON :A subsidiary of Fidelity Investments has filed a lawsuit accusing technology company Broadcom of threatening to cut off its access to key software that has become central to the financial firm's systems, creating the risk of "massive outages" and trading disruptions unless a judge intervenes to stop it. Fidelity Technology Group, a subsidiary of the Boston-based asset manager, in court filings made public on Friday in Suffolk County Superior Court alleged its business faces "enormous"