[counters] add --dsrouter switch (#5543)

We added this to `dotnet-gcdump` in fcaeae3 and `dotnet-trace` in
a29f26d.

This allows `dsrouter` to be launched, such as:

    > dotnet-counters collect --dsrouter android
For finer control over the dotnet-dsrouter options, run it separately
and connect to it using -p

WARNING: dotnet-dsrouter is a development tool not intended for
production environments.

How to connect current dotnet-dsrouter pid=40432 with android device and
diagnostics tooling.
Start an application on android device with ONE of the following
environment variables set:
    [Default Tracing]
    DOTNET_DiagnosticPorts=127.0.0.1:9000,nosuspend,connect
    [Startup Tracing]
    DOTNET_DiagnosticPorts=127.0.0.1:9000,suspend,connect
See
https://learn.microsoft.com/en-us/dotnet/core/diagnostics/dotnet-dsrouter
for additional details and examples.

    info: dotnet-dsrouter-40432[0]
        Starting dotnet-dsrouter using pid=40432
    info: dotnet-dsrouter-40432[0]
        Looking for Android NDK...
    info: dotnet-dsrouter-40432[0]
        Looking for Android SDK...
    info: dotnet-dsrouter-40432[0]
Starting IPC server (dotnet-diagnostic-dsrouter-40432) <--> TCP server
(127.0.0.1:9001) router.
--counters is unspecified. Monitoring System.Runtime counters by
default.

Documentation PR:
* dotnet/docs#47874

Author: jonathanpeppers

src/Tools/dotnet-counters/CounterMonitor.cs

@@ -247,6 +247,10 @@ public async Task<ReturnCode> Monitor(
                 _stdError.WriteLine(e.Message);
                 return ReturnCode.ArgumentError;
             }
+            finally
+            {
+                DsRouterProcessLauncher.Launcher.Cleanup();
+            }
         }
         public async Task<ReturnCode> Collect(
             CancellationToken ct,
@@ -350,6 +354,10 @@ public async Task<ReturnCode> Collect(
                 _stdError.WriteLine(e.Message);
                 return ReturnCode.ArgumentError;
             }
+            finally
+            {
+                DsRouterProcessLauncher.Launcher.Cleanup();
+            }
         }
 
         private static void ValidateNonNegative(int value, string argName)

src/Tools/dotnet-counters/Program.cs

@@ -33,7 +33,8 @@ private static Command MonitorCommand()
                 MaxHistogramOption,
                 MaxTimeSeriesOption,
                 DurationOption,
-                ShowDeltasOption
+                ShowDeltasOption,
+                DSRouterOption
             };
 
             monitorCommand.TreatUnmatchedTokensAsErrors = false; // see the logic in Main
@@ -50,7 +51,7 @@ private static Command MonitorCommand()
                 maxTimeSeries: parseResult.GetValue(MaxTimeSeriesOption),
                 duration: parseResult.GetValue(DurationOption),
                 showDeltas: parseResult.GetValue(ShowDeltasOption),
-                dsrouter: string.Empty
+                dsrouter: parseResult.GetValue(DSRouterOption)
             ));
 
             return monitorCommand;
@@ -72,7 +73,8 @@ private static Command CollectCommand()
                 ResumeRuntimeOption,
                 MaxHistogramOption,
                 MaxTimeSeriesOption,
-                DurationOption
+                DurationOption,
+                DSRouterOption
             };
 
             collectCommand.TreatUnmatchedTokensAsErrors = false; // see the logic in Main
@@ -90,7 +92,7 @@ private static Command CollectCommand()
                 maxHistograms: parseResult.GetValue(MaxHistogramOption),
                 maxTimeSeries: parseResult.GetValue(MaxTimeSeriesOption),
                 duration: parseResult.GetValue(DurationOption),
-                dsrouter: string.Empty));
+                dsrouter: parseResult.GetValue(DSRouterOption)));
 
             return collectCommand;
         }
@@ -139,6 +141,12 @@ private static Command CollectCommand()
                 " To discover well-known provider and counter names, please visit https://learn.microsoft.com/dotnet/core/diagnostics/built-in-metrics."
             };
 
+        private static readonly Option<string> DSRouterOption =
+            new("--dsrouter")
+            {
+                Description = @"The dsrouter command to start. Value should be one of ios, ios-sim, android, android-emu. Run `dotnet-dsrouter -h` for more information."
+            };
+
         private static Command ListCommand()
         {
             Command listCommand = new(