add option for -onlynet=onion in bails-menu

[BenWestgate]

In ordinary circumstances there is a privacy benefit of using -onlynet=onion. However because it is more fragile in hostile network circumstances and may need console commands to be as resilient as the default, it is not set on. Users who need the maximum in transaction broadcast privacy can turn this on or off in the bails-menu after a debriefing.
Suggestion by @epiccurious .

related to #5

[BenWestgate]

Sure! Here's an example Zenity dialog that presents the option to enable -onlynet=onion or leave it at defaults:

zenity --question --title='Network Settings' --width=400 --text='Bails offers different network settings for connecting to the Bitcoin network. By default, Bails connects to both the clearnet and Tor (onion) peers, providing a balance between usability and privacy.

Would you like to enhance your privacy by connecting exclusively to Tor (onion) peers with reduced clearnet exposure? This will increase your privacy but may limit your network diversity and can be less stable if you have limited Tor peers.'

if [ $? = 0 ]; then
    # User chose to enable -onlynet=onion
    # Add your code here to set the option and inform the user about potential implications.
    # You can also provide instructions on how to revert to the default setting if desired.
    zenity --info --title='Network Settings Updated' --text='You have chosen to connect exclusively to Tor (onion) peers. Your network settings have been updated to enhance your privacy. Please note that this may affect network diversity and stability.'

else
    # User chose to leave it at defaults
    zenity --info --title='Network Settings Unchanged' --text='You have chosen to keep the default network settings. Bails will continue to connect to both clearnet and Tor (onion) peers, providing a balance between usability and privacy.'

fi

This dialog presents a clear explanation of the network settings and their implications, allowing non-technical users to make an informed decision based on their privacy preferences. It also includes a message for each option to confirm the user's choice and provide feedback on the updated settings.

[BenWestgate]

Enhancement added to bails-menu re-write. Enjoy @epiccurious

e13ffb8