Revert recent merges affecting chat session functionality (#287734)

* Revert "Merge pull request #287668 from mjbvz/dev/mjbvz/eventual-sparrow"

This reverts commit 81f7af4b9f20f2746d58e2ca28e4f686856df81b, reversing
changes made to 85a14f966c3ad1b7dbe5c1275a235a57fac1b5d7.

* Revert "Merge pull request #286642 from microsoft/dev/mjbvz/chat-session-item-controller"

This reverts commit b39ecc3960ec91b2ce85518d44e3e8a323b7f4a6, reversing
changes made to 45aced59351aa73fd1bc002f64ab4a0c13ba68a9.