Complete CSIP and CAP

[zxzxwu]

Changes:

• RSI generation
• SIRK encryption
• Delegated SIRK reader
• Prand and random address generation

TODO:

• Encrypted SIRK. Requiring a change: Complete CSIP and CAP #374 (comment), so it would be implemented in another CL.

Test:

• csip_test, cap_test
• Manually pairing with Android CSIS client

[zxzxwu]

One question: LTK and LK must be retrieved asynchronously, but GATT read must be synchronous. How to resolve this?

[barbibulle]

One question: LTK and LK must be retrieved asynchronously, but GATT read must be synchronous. How to resolve this?I

I have a WIP local branch that implements support for async characteristic values (both read and write). I'll polish it off and submit a PR shortly, that should solve your use case here.

[zxzxwu]

We may merge this CL first, and then create another PR when the async GATT read is ready.

[barbibulle]

Maybe this function should return an Address, with the right address type? (Also, this is a function that uses crypto, but isn't a crypto function itself, so maybe it should live somewhere else?

[zxzxwu]

I think rand / prand is also considered crypto somehow? But yes, they're better to be classmethods of Address. The only exception is prand - hosting it in hci/Address is not very proper, but there isn't a module more proper than crypto(from my point of view).

[zxzxwu]

Moving address methods to #379