RepositorySimulator: Include "refresh" in dump directory name

This way it's maybe more obvious that each repository version
is dumped at the time of each client refresh.

Signed-off-by: Jussi Kukkonen <[email protected]>

README.md

@@ -87,8 +87,8 @@ we can now run the test:
     --repository-dump-dir /tmp/test-repos   # dump repository contents
 
 # take a look at the repository targets.json that got debug dumped
-cat /tmp/test-repos/test_targets_version/1/targets.json
-cat /tmp/test-repos/test_targets_version/1/snapshot.json
+cat /tmp/test-repos/test_targets_version/refresh-1/targets.json
+cat /tmp/test-repos/test_targets_version/refresh-1/snapshot.json
 ```
 
 The metadata looks as expected (targets version is 7) so we can add a modification to the end of the test:
@@ -110,8 +110,8 @@ Running the test again results in a second repository version being dumped (each
     --repository-dump-dir /tmp/test-repos   # dump repository contents
 
 # take a look at targets versions in both snapshot versions that got debug dumped
-cat /tmp/test-repos/test_targets_version/1/snapshot.json
-cat /tmp/test-repos/test_targets_version/2/snapshot.json
+cat /tmp/test-repos/test_targets_version/refresh-1/snapshot.json
+cat /tmp/test-repos/test_targets_version/refresh-2/snapshot.json
 ```
 
 The repository metadata looks as expected (but not spec-compliant) so we can add some asserts for client behaviour now.

tuf_conformance/repository_simulator.py

@@ -467,7 +467,7 @@ def debug_dump(self) -> None:
             return
 
         self.dump_version += 1
-        dest_dir = os.path.join(self.dump_dir, str(self.dump_version))
+        dest_dir = os.path.join(self.dump_dir, f"refresh-{self.dump_version}")
         os.makedirs(dest_dir, exist_ok=True)
 
         for ver in range(1, len(self.signed_roots) + 1):