Update go1.21 and CI (#315)

* Update to go 1.21

Use `atomic.Bool` stdlib instead of including our own.

Include `tools\mkwinsyscall` updates from go-winio/283 to switch to
`syscallN`.
Note: removed `// TODO` about `print`/`ln`, since the latter adds spaces
between args when printing, which is undesired.

Also update CI to run steps on windows-2022 instead of windows-2019,
similar to our hcsshim CI.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* PR: simplify type checking

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

---------

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

internal/socket/socket.go

@@ -156,9 +156,7 @@ func connectEx(
 	bytesSent *uint32,
 	overlapped *windows.Overlapped,
 ) (err error) {
-	// todo: after upgrading to 1.18, switch from syscall.Syscall9 to syscall.SyscallN
-	r1, _, e1 := syscall.Syscall9(connectExFunc.addr,
-		7,
+	r1, _, e1 := syscall.SyscallN(connectExFunc.addr,
 		uintptr(s),
 		uintptr(name),
 		uintptr(namelen),
@@ -166,8 +164,8 @@ func connectEx(
 		uintptr(sendDataLen),
 		uintptr(unsafe.Pointer(bytesSent)),
 		uintptr(unsafe.Pointer(overlapped)),
-		0,
-		0)
+	)
+
 	if r1 == 0 {
 		if e1 != 0 {
 			err = error(e1)