faces/totp: update watch face logic for new struct

faces/totp: update watch face logic for new struct

Using the new structured TOTP record data structure
allows the TOTP watch face to statically and implicitly
compute the total number of defined TOTP records.

Users can now simply add new keys and records in the designated area
and the watch face will compile and automatically use them with no need
to maintain a separate array size variable. Less chance of mistakes.