Repo simulator: make delegates() to all_targets()

Modify RepositorySimulator function delegates() to all_targets(), so
that all targets can be traversed and updated with one cycle when
calling update_snapshot() (which is the only use case for now for
delegates()).

Signed-off-by: Martin Vrachev <mvrachev@vmware.com>

tests/repository_simulator.py

@@ -124,7 +124,8 @@ def snapshot(self) -> Snapshot:
     def targets(self) -> Targets:
         return self.md_targets.signed
 
-    def delegates(self) -> Iterator[Tuple[str, Targets]]:
+    def all_targets(self) -> Iterator[Tuple[str, Targets]]:
+        yield "targets", self.md_targets.signed
         for role, md in self.md_delegates.items():
             yield role, md.signed
 
@@ -264,8 +265,7 @@ def update_timestamp(self):
         self.timestamp.version += 1
 
     def update_snapshot(self):
-        self.snapshot.meta["targets.json"].version = self.targets.version
-        for role, delegate in self.delegates():
+        for role, delegate in self.all_targets():
             self.snapshot.meta[f"{role}.json"].version = delegate.version
 
             if self.compute_metafile_hashes_length: