The shim "start" helper returns the named pipe address before the
daemon process has created the pipe via winio.ListenPipe(). On busy
Windows systems, containerd may try to connect before the pipe exists.
Add awaitPipeReady() — the start helper now polls the pipe address
(up to 5s, 10ms intervals) before writing the bootstrap result to
stdout. This follows hcsshim's readiness pattern where the shim
verifies its endpoint is ready before signaling the parent.
As a safety net, also parameterize makeConnection() with a dialer so
binary.Start() uses AnonDialer (retry) for new shims while loadShim()
keeps AnonReconnectDialer (fail-fast) for reconnects per #3659.
On Unix, awaitPipeReady() is a no-op: domain sockets appear atomically.
Signed-off-by: Esteban Ginez <esteban.ginez@docker.com>
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