spice: drop input_stream_read_thread*()
spice: drop input_stream_read_thread*()

We can now use g_input_stream_read_all_async()
which wasn't available before.

On Unix, the stream is pollable and thus the read happens
in the main context.
On Windows, read is implicitly done in a thread.

Signed-off-by: Jakub Janků <e6d62f7189d9c45efd907e4f2baf6f535f551138@redhat.com>

GNOME/phodav,GNOME/phodav