fix(core): handle killing child processes of continuous tasks on Windows (#31296)

This PR fixes an issue where running `nx e2e <proj>` on Windows does not
kill the underlying dev/preview server when the e2e task ends.

Repro:
1. `npx create-nx-workspace@latest repro --preset=react-monorepo
--e2eTestRunner=playwright --appName=demo`
2. `cd repro && npx nx e2e demo-e2e`

This will leave the preview server running on port `4300`, and you have
to `netstat -ano | findstr :4300` to find the PID and kill it.

https://www.loom.com/share/fcbea53cdff543a98f4d4c8377027ee0

## Current Behavior
Continuous task does not kill the process correctly once discrete task
ends.

## Expected Behavior
Processes are killed correctly once task is done running.

## Related Issue(s)
<!-- Please link the issue being fixed so it gets closed when this is
merged. -->

Fixes #31235

packages/nx/src/executors/run-commands/running-tasks.ts

@@ -359,21 +359,15 @@ class RunningNodeProcess implements RunningTask {
 
   kill(signal?: NodeJS.Signals): Promise<void> {
     return new Promise<void>((res, rej) => {
-      if (process.platform === 'win32') {
-        if (this.childProcess.kill(signal)) {
-          res();
-        } else {
-          rej('Unable to kill process');
-        }
-      } else {
       treeKill(this.childProcess.pid, signal, (err) => {
-          if (err) {
+        // On Windows, tree-kill (which uses taskkill) may fail when the process or its child process is already terminated.
+        // Ignore the errors, otherwise we will log them unnecessarily.
+        if (err && process.platform !== 'win32') {
           rej(err);
         } else {
           res();
         }
       });
-      }
     });
   }