Writing to fs via stream hungs

[ruifigueira]

To reproduce the error:

./bazel-bin/src/workerd/server/workerd serve ./samples/nodejs-compat-fs-yazl/config.capnp

and then curl localhost:8080. It will get a Internal Server Error and in workerd we get:

kj/exception.c++:357: warning: llvm-symbolizer was not found. To symbolize stack traces, install it in your $PATH or set $LLVM_SYMBOLIZER to the location of the binary. When running tests under bazel, use `--test_env=LLVM_SYMBOLIZER=<path>`.
workerd/server/server.c++:5081: error: Uncaught exception: workerd/io/io-context.c++:1328: failed: remote.jsg.Error: The Workers runtime canceled this request because it detected that your Worker's code had hung and would never generate a response. Refer to: https://developers.cloudflare.com/workers/observability/errors/
stack: 10199ef3c 1019a09f8 1019a2ce7 1019a2bd3 1019a27cf 106e498cf 106e28567 10153da34 10153e8a0 101541abc 101544454 10025ec57 102793a17 1027984fb 10279c357 1026d5608