Add TCS context handling.

The TSS specification defines a TCS layer that facilitates communication
between the TPM and the TSP. The TCS layer also requires context similar to
that of the TCS.
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: I73510d50f922e1a2ce70037e43067f717d8310f3
Reviewed-on: https://gerrit.chromium.org/gerrit/65711
Reviewed-by: Darren Krahn <dkrahn@chromium.org>
Commit-Queue: Sarah Harvey <saharvey@chromium.org>
Tested-by: Sarah Harvey <saharvey@chromium.org>
5 files changed