Extract handle sweep thread fields from __wt_connection_impl (lines 910-916) into a new WT_CONN_SWEEP structure. This includes sweep_session, sweep_tid, sweep_tid_set, sweep_cond, sweep_idle_time, sweep_interval, and sweep_handles_min. Access will be via conn->sweep.<field>.

Files affected

• src/include/connection.h — Define WT_CONN_SWEEP structure and replace individual sweep fields
• src/conn/conn_sweep.c — Update handle sweep thread code
• Any files that reference sweep configuration

Definition of Done

• New WT_CONN_SWEEP structure defined in connection.h containing all sweep fields
• All sweep fields removed from __wt_connection_impl and replaced with single sweep member
• All references updated from conn->sweep_session to conn->sweep.session, etc.
• Code compiles cleanly with no warnings
• All existing tests pass
• Grep confirms no stale references to old sweep field paths