chore: add extra output in CLI integ tests (#24499)

Trying to diagnose what is happening in CodeBuild when the integration
tests run for V2, as something appears to hang. Using
`process.stderr.write` allows bypassing `jest`'s hijacking of
`console.log` and `console.error`, so these traces _always_ show.

Author: RomainMuller

packages/@aws-cdk-testing/cli-integ/lib/integ-test.ts

@@ -36,6 +36,7 @@ export function integTest(
     output.write('================================================================\n');
 
     try {
+      process.stderr.write(`▶️ [INTEG TEST::${name}] Starting...\n`);
       return await callback({
         output,
         randomString: randomString(),
@@ -44,13 +45,16 @@ export function integTest(
         },
       });
     } catch (e) {
+      process.stderr.write(`💥 [INTEG TEST::${name}] Failed: ${e}\n`);
       output.write(e.message);
       output.write(e.stack);
       // Print output only if the test fails. Use 'console.log' so the output is buffered by
       // jest and prints without a stack trace (if verbose: false).
       // eslint-disable-next-line no-console
       console.log(output.buffer().toString());
       throw e;
+    } finally {
+      process.stderr.write(`⏹️ [INTEG TEST::${name}] Done.\n`);
     }
   }, timeoutMillis);
 }