fix: chdir to parent cwd in child runner

When using the runner on Windows, the cwd of the child process seems to
be the directory where `code.exe` is located, rather than the directory
where it was started. On Linux and macOS, the cwd is correctly set to
the directory from which Jest was launched.

To ensure consistency between platforms, this fix will always set the
child process' cwd to the cwd of the parent.

This is mostly to fix an issue where `runCLI` within the child process
cannot find a passed `--config` path since the cwd doesn't match what's
expected by Jest. This can be replicated by running the following:

```shell
cd e2e/passing-tests
yarn jest --config ../passing-tests/jest.config.js
```

This will work on Linux and macOS, but will not work on Windows before
this fix. After this fix, it will work correctly.

packages/jest-runner-vscode/src/child/runner.ts

@@ -23,11 +23,16 @@ export async function run(): Promise<void> {
   )
 
   try {
-    const { PARENT_JEST_OPTIONS } = process.env
+    const { PARENT_JEST_OPTIONS, PARENT_CWD } = process.env
 
     if (!PARENT_JEST_OPTIONS) {
       throw new Error('PARENT_JEST_OPTIONS is not defined')
     }
+
+    if (PARENT_CWD) {
+      process.chdir(PARENT_CWD)
+    }
+
     const options = JSON.parse(PARENT_JEST_OPTIONS) as RemoteTestOptions
     const jestOptions = [
       ...options.args,