How many cardiologists handle internal med or primary care concerns for their patients?

Not many. Not usually. In most instances where you can a cardiologist you can find extremely good primary care physicians. While one stop health shopping sounds convenient it is often not in the patients best interest long term especially if that place is a specialists office.
Usually they don't. Most cardiologists pretty much focus in on problems of the heart. There are not enough of them and they are extremely overworked. They usually will handoff any primary care issues to either an internist or a family physician. I wouldn't expect them to deal with primary care problems.