Add TSP context handling.

The TSS specification defines a TSP layer that is accessible through a C API.
Each connection the TSP makes to the TCS requires a context, thus context
handling is needed before any other functions are implemented.

The following has been implemented:
 - context management (creation, deletion)
 - context resource management

Unit tests are also provided testing these two things.

BUG=chromium:254742
TEST=Compiles successfully and passes unit tests.

Change-Id: I52fe88764a6fd53375bc98181d4b730e891c6c32
Reviewed-on: https://gerrit.chromium.org/gerrit/60829
Reviewed-by: Darren Krahn <dkrahn@chromium.org>
Commit-Queue: Sarah Harvey <saharvey@chromium.org>
Tested-by: Sarah Harvey <saharvey@chromium.org>
14 files changed