Add preference to hide specific VPN configurations

[Timac]

There are some VPN configurations that you might not want to see in VPNStatus:

• third-party content filter configurations like Little Snitch. You probably have no reason to manually enable or disable them with VPNStatus
• ghost VPN configurations. For example, I see an old VPN configuration that I can't delete after upgrading to macOS Ventura 13.3. This old configuration is cached in /Library/Preferences/com.apple.networkextension.plist which is SIP protected. Trying to manually remove the entry in the plist resulted in more issues.

At the moment, VPNStatus contains a hardcoded blocklist with Little Snitch. Exposing this blocklist as a preference would let a user hide the ghost VPN configurations as well as other third-party content filter configurations like Little Snitch.

Example of modifying the preference from the command line:

defaults write org.timac.VPNStatus IgnoredVPNs "Little Snitch,HiddenVPN,AnotherHiddenVPN"