Nest multiple 'resolving hash xxx' steps under a single super step.

scripts/slave/recipes/bisection/android_bisect.expected/local_basic_recipe_basic_device.json

 [
   {
     "cmd": [],
     "name": "ensure_goma"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::cipd]/resources/bootstrap.py",
@@ skipping 1904 matching lines @@
     ],
     "cwd": "[BUILDER_CACHE]/android_one_perf_bisect",
     "name": "Gathering reference values.Recipe failed. Reason: Testing the \"good\" revision failed",
     "~followup_annotations": [
       "@@@STEP_NEST_LEVEL@1@@@",
       "@@@STEP_LOG_LINE@python.inline@import sys; sys.exit(1)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
+    "cmd": [],
+    "cwd": "[BUILDER_CACHE]/android_one_perf_bisect",
+    "name": "Resolving hashes"
+  },
+  {
     "cmd": [
       "git",
       "footers",
       "--position",
       "fc6dfc7ff5b1073408499478969261b826441144"
     ],
     "cwd": "[BUILDER_CACHE]/android_one_perf_bisect/src",
-    "name": "resolving hash fc6dfc7ff5b1073408499478969261b826441144",
-    "stdout": "/path/to/tmp/"
+    "name": "Resolving hashes.resolving hash fc6dfc7ff5b1073408499478969261b826441144",
+    "stdout": "/path/to/tmp/",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@1@@@"
+    ]
   },
   {
     "cmd": [],
     "cwd": "[BUILDER_CACHE]/android_one_perf_bisect",
     "name": "Debug Info",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@Debug Info@bisector.lkgr: RevisionState(rev=chromium@e28dc0d49c, values=[], mean_value=None, std_dev=None)@@@",
       "@@@STEP_LOG_LINE@Debug Info@bisector.fkbr: RevisionState(rev=chromium@fc6dfc7ff5, values=[], mean_value=None, std_dev=None)@@@",
       "@@@STEP_LOG_LINE@Debug Info@@@@",
       "@@@STEP_LOG_LINE@Debug Info@Revision       Values         @@@",
@@ skipping 235 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.remove(report)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]