[v14.x] fs: remove custom Buffer pool for streams
The performance benefit of using a custom pool are negligable. Furthermore, it causes problems with Workers and transferrable. Rather than further adding complexity for compat with Workers, just remove the pooling logic.
Refs: https://github.com/nodejs/node/issues/33880#issuecomment-644430693 Fixes: https://github.com/nodejs/node/issues/31733