benchmark: use unique filenames in fs benchmarks

Use a unique file name for each benchmark. Running benchmarks
simultaneously may be a bit of an unusual use case, but there are use
cases, such as stress testing `test/parallel/test-benchmark-fs.js`.

PR-URL: #16776
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

benchmark/fs/read-stream-throughput.js

@@ -3,7 +3,8 @@
 
 const path = require('path');
 const common = require('../common.js');
-const filename = path.resolve(__dirname, '.removeme-benchmark-garbage');
+const filename = path.resolve(__dirname,
+                              `.removeme-benchmark-garbage-${process.pid}`);
 const fs = require('fs');
 const assert = require('assert');
 

benchmark/fs/readfile.js

@@ -5,7 +5,8 @@
 
 const path = require('path');
 const common = require('../common.js');
-const filename = path.resolve(__dirname, '.removeme-benchmark-garbage');
+const filename = path.resolve(__dirname,
+                              `.removeme-benchmark-garbage-${process.pid}`);
 const fs = require('fs');
 
 const bench = common.createBenchmark(main, {

benchmark/fs/write-stream-throughput.js

@@ -3,7 +3,8 @@
 
 const path = require('path');
 const common = require('../common.js');
-const filename = path.resolve(__dirname, '.removeme-benchmark-garbage');
+const filename = path.resolve(__dirname,
+                              `.removeme-benchmark-garbage-${process.pid}`);
 const fs = require('fs');
 
 const bench = common.createBenchmark(main, {