InitializeHostDefinedRealm seems to be the most promising candidate.

Notice that for ScriptEvaluation, you need a script record, so you'd usually call ParseScript first. But for that, you need a realm, which indeed would be created via InitializeHostDefinedRealm.

Of course, a host is free not to use any of these in theory. It might restore the entire state of the global execution context from a static image on disk, and begin execution in the middle of whatever was running when the state was frozen.