Revert "Introduce SessionCallbackLink"

This reverts commit 8eee83e59412ff4a281e6c5170881db347627c99.

Reason for revert: Another CL will be uploaded which makes the APIs public, not @SystemApi.

Bug: 121239657
Change-Id: I0537ffd487ab6889213b8917615156caaec17eb5
11 files changed