Issues with `js_interop_tests`

[cowlicks]

• the test js_interop_rcns_simple_client_writer was hanging frequently. ignore'd in maintenance  #20
• there is a rare hang in js_interop_ncrs_simple_server_writer
• there is an occasional fail in js_interop_rcns_simple_server_writer

These should be fixed. When this work is done, we might want to consider switching the code to use tokio at the same time.