Assisted Keys: MFP to XFP

[Parsh]

Task Description We'll be sending XFP as the master fingerprint as it resolves the following issues:

• Allows multiple assisted keys(of the same kind) for the same app, as key management uses mfp as the main identifier(and currently all SS and IKS have the same mfp)
• Inheritance doc for all users currently shows the same fingerprint(as they have the same mfp), while they should have been unique.
• IKS and SS are currently replacing each other on the live app(they share the same mfp on mainnet).

[cakesoft-swati]

• Closing this issue as discussed with dev.