Add confirmation UI support libaray

Includes:

A light weight CBOR generator
  This patch adds a header only CBOR generator and unit tests.
  It allows expressing CBOR datastructures in C++ for subsequent
  serialization. The implementation performs no memory allocation
  and only depends on stdint.h (for (u)intx_t) and stddefs.h (for size_t).
  It is tailored for use in constrained environments such as TEEs.

Convenience method for generating a SHA256 HMAC

Bug: 63928580
Test: android.hardware.confirmationui@support-lib-tests
Change-Id: I1d93a85503f861281e71e09b1ede5cbb74219694