Use a custom tick frequency

[bigspider]

os_io_seph_cmd_setup_ticker allows to set the frequency of the ticker event, which defaults at 100ms.

More frequent tickers (e.g. every 10ms) might be helpful to fine-tune the UX and improve performance of async tasks introduced in #248.

Caveat: os_io_seph_cmd_setup_ticker is not currently implemented in speculos.