Add support for 'data-ciphers-fallback' option

This is a new version !70 (closed). I have:

• Rebased !70 (closed) to the current main.
• Verified that previous comments have been resolved.
• Added GUI for both data-ciphers and data-ciphers-fallback as requested.

Unfortunately, the pipeline fails, but apparently there is a general problem with the runner that has nothing to do with my changes.

Requested changes to the GUI introduced new strings. I guess the catalog should be regenerated, or how do you handle that for this project?

Note that I have zero experience with GTK, so please bear with me on the GUI stuff.