trusty: Retrieve coverage PCs from coverage record

Adds the ability to retrieve and save program counter information from
the trusty coverage record data. PC information is saved to a .sancov
file, parseable by the LLVM sancov tool. Sancov can then symbolize and
display this coverage information for consumption by humans.

Adds a sancov dump to the libtrusty_coverage_test for testing.

Bug: 175221942
Test: atest libtrusty_coverage_test
Test: Retrieve sancov file and manually symbolize with sancov
Change-Id: I342ea2ca9abb87986b2904ff69415544ee6070fc