Fix Audit security comments

[ajinkyaraj-23]

in app/src/apdu_sign.c : 486, buffer’s content as to be zeroized (i.e.,cleared). For this, only the buffer size was reset to zero. In doing so, the data persists in memory, with the risk of being read by another channel.

• Reset the buffer and not just its size.
• Initialize pressed_right in ui_stream.c and ui_stream_nbgl.c
• Fix TODO/NOTE and other comments - check app/src/ui_stream_nbgl.c: 352-354 and app/src/globals.h: 122
• Remove redundant check for global.step in app/src/apdu_sign.c : 486
• <=0 check is not correct for unsigned int. Fix at app/src/parser/operation_parser.c: 418
• fix printf format specifier incompatibility at app/src/apdu_sign.c : 585