[StreamExecutor] Allow HostExecutor users to control the stack sizes of threads used for HostStream via. Also include non_portable_tags in the keys used when creating an Executor. There seems to be no good reason that it is omitted. Will fix https://github.com/google/jax/issues/432 when included in a jaxlib release. PiperOrigin-RevId: 309472318 Change-Id: Ia2535616047390d6bf6f2da82a666a321dcc9f5d