Adds a couple more measures to the benchmarking app

mojo/tools/data/rtt_benchmarks

 # This file contains a list of Mojo benchmarks. For description of the file
 # format, see `mojo_benchmark --help`.
 
 benchmarks = [
   {
     'name': 'C++ <=> C++ IPC Round Trip Time',
     'app': 'https://core.mojoapps.io/echo_benchmark.mojo',
     'duration': 10,
     'measurements': [
       'avg_duration/echo_benchmark/ping',
+      'dist_duration/echo_benchmark/ping',
     ],
     'shell-args': [
       '--args-for=https://core.mojoapps.io/echo_benchmark.mojo --early-tracing',
     ]
   },
   {
     'name': 'Dart <=> Dart IPC Round Trip Time',
     'app': 'https://core.mojoapps.io/dart_rtt_benchmark.mojo',
     'duration': 10,
     'measurements': [
       'avg_duration/mojo_rtt_benchmark/ping',
+      'dist_duration/mojo_rtt_benchmark/ping',
     ]
   },
   {
     'name': 'Dart <=> C++ IPC Round Trip Time',
     'app': 'https://core.mojoapps.io/dart_rtt_benchmark.mojo',
     'duration': 10,
     'measurements': [
       'avg_duration/mojo_rtt_benchmark/ping',
+      'dist_duration/mojo_rtt_benchmark/ping',
     ],
     'shell-args': [
       '--args-for=https://core.mojoapps.io/dart_rtt_benchmark.mojo --cpp-server',
     ]
   },
   {
     'name': 'Dart Isolate Message Round Trip Time',
     'app': 'https://core.mojoapps.io/dart_isolate_rtt_benchmark.mojo',
     'duration': 10,
     'measurements': [
       'avg_duration/isolate_rtt_benchmark/ping',
+      'dist_duration/isolate_rtt_benchmark/ping',
     ]
   },
 ]