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/interop/zsyscall_windows.go

@@ -33,9 +33,6 @@ func errnoErr(e syscall.Errno) error {
 	case errnoERROR_IO_PENDING:
 		return errERROR_IO_PENDING
 	}
-	// TODO: add more here, after collecting data on the common
-	// error values see on Windows. (perhaps when running
-	// all.bat?)
 	return e
 }
 
@@ -46,6 +43,6 @@ var (
 )
 
 func coTaskMemFree(buffer unsafe.Pointer) {
-	syscall.Syscall(procCoTaskMemFree.Addr(), 1, uintptr(buffer), 0, 0)
+	syscall.SyscallN(procCoTaskMemFree.Addr(), uintptr(buffer))
 	return
 }