When a Test has occurred previously and a call graph is generated, we need to be able to force TI to either delete the pre-existing call graph, or to force generate a new call graph.

This is because a pre-existing callgraph on a commit may exist, and we want to force a refresh on it because there may be outstanding tests that exist in a different pipeline that the current pipeline would not be aware of.

There are other scenarios where we would want TI to force refresh the call graph/force a refresh of all tests, but above is just one of them.