Display public key on "save address" (set slot) screen

[psiemens]

When saving a new address to the device, the "Set Slot" verification screen currently only shows the Flow address value, but it should also display the associated public key for that path.

This allows the user to check both the address and public key against an on-chain source in order to verify that they are paired correctly.

[pgebheim]

@relatko Did your commit earlier in 0c7f4dd fix this issue or was that just related to this issue?

[relatko]

@pgebheim The commit was just rollback commit. Set slot path still does not show public key, just derivation address. See snapshots from current master:
https://github.com/onflow/ledger-app-flow/tree/master/tests_speculos/test-basic-slot-status-full

What however has been done is that if an address is stored on slot 0, then both getPublicKey call and an item in the menu allow to review both address and public key. To see how this interaction work at the moment you can review these snapshots
https://github.com/onflow/ledger-app-flow/tree/master/tests_speculos/test-menu

If the functionality as described here is still desired it is fairly straightforward task requiring one to two days of work (it may be slightly harder than it looks at the first glance, but still fairly easy).