WASHINGTON — Health care providers are pushing the federal government to scrap the payment plan for medical services, preferring instead one payment for a patient's entire care instead of separate fees for each item. Instead of fee-for-service medicine, in which a provider receives a payment for every test, procedure and visit, providers want the government — or states or private payers — to pay for treatment as a whole. In theory, physicians would provide treatments that have been proven to work but are also cost-effective.