This adds `_IRQ_GET_SECRET` and `_IRQ_SET_SECRET` events to allow the BT
stack to request the Python code retrive/store/delete secret key data. The
actual keys and values are opaque to Python and stack-specific.
Only NimBLE is implemented (pending moving btstack to sync events). The
secret store is designed to be compatible with BlueKitchen's TLV store API.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
c4d08aa4e3