private boolean isSnapshot() {
		return !provider.isConnected();
	}
Signals that something major has changed for the program and we don't know where, so clear
all cached functions for the given program.

BLEH!: I don't like clearing the cache this way...another options is to mark all cached
values as stale, somehow. If we did this, then when the view reuses the cached data, it could
signal to the user that the graph is out-of-date.

@param program the program
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/mvc/FGController.java