Fix Windows wrong output

[w6rsty]

Due to the fact that netsh output is based on the system's language settings, simply using "completed successfully" to check the result will not work in other languages

wifi-rs/src/connectivity/providers/windows.rs

Lines 50 to 52 in c46c05d

	if !String::from_utf8_lossy(&output.stdout)
	.as_ref()
	.contains("completed successfully")

To address this issue while keeping the solution simple, I use the user-provided ssid to match the output of
netsh wlan show interfaces

I've also added a check to see if the system is already connected to the specified WLAN