trunks: Added PolicySession and SessionManager

Added SessionManager class to keep track of TPM
AuthorizationSessions.
Made HmacSession and PolicySession depend on SessionManager.
Removed the AuthorizationSession class.

BUG=chromium:472846
TEST=unit and trunks_client --regression_test

Change-Id: I9b9c4b012cf33a6fbc50d6c12b0edece85033dfb
Reviewed-on: https://chromium-review.googlesource.com/265472
Tested-by: Utkarsh Sanghi <usanghi@chromium.org>
Reviewed-by: Darren Krahn <dkrahn@chromium.org>
Commit-Queue: Utkarsh Sanghi <usanghi@chromium.org>
33 files changed