Add utilities to deal with software keyblobs

Add code (adapted from system/keymint/common/src/keyblob/legacy.rs)
which parses keyblobs in the format produced by the previous C++
reference implementation of KeyMint.

Bug: 283077822
Bug: 296403357
Test: tested with ARC upgrade, see b/296403357
Change-Id: I519eed0ac968d5c2595f95609ffadede5d2d2677
4 files changed