camera: Remove session_hal_buf_manager flag

Note: mUseHalBufManager in Camera3Device will be removed after initial flag
removal.

Bug: 365555557

Test: Camera CTS, GCA

Flag: EXEMPT flag removal

Change-Id: I88975ca675b6ba753112e700fa28701a3acc121e
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>