refactor(common): move scanner/heal domain contracts into dedicated crates
crates/common carried ~5.6K lines of scanner/heal domain code (metrics.rs,
heal_channel.rs, last_minute.rs) parked there to break dependency cycles;
every scanner type change recompiled all 11 rustfs-common dependents.
Pure move, zero renames, zero shape changes (backlog#1843):
- New crate rustfs-heal-contracts receives heal_channel.
- New crate rustfs-scanner-contracts receives metrics, last_minute, and the
GLOBAL_INIT_TIME trio (metrics::report() reads it as the current-cycle
fallback, so it must live below the shim to avoid a dependency cycle).
- rustfs-common re-exports everything at the old paths as a transitional
shim; consumers migrate crate by crate, then the shims are deleted.
houseme