refactor(common): move scanner/heal contracts into dedicated crates (#6615)

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.

Cargo.lock

@@ -9390,13 +9390,10 @@ dependencies = [
 name = "rustfs-common"
 version = "1.0.0-rc.3"
 dependencies = [
- "chrono",
  "hotpath",
- "jiff",
  "metrics",
- "rmp-serde",
- "serde",
- "serde_json",
+ "rustfs-heal-contracts",
+ "rustfs-scanner-contracts",
  "smallvec",
  "tokio",
  "tonic",
@@ -9684,6 +9681,15 @@ dependencies = [
  "walkdir",
 ]
 
+[[package]]
+name = "rustfs-heal-contracts"
+version = "1.0.0-rc.3"
+dependencies = [
+ "serde",
+ "tokio",
+ "uuid",
+]
+
 [[package]]
 name = "rustfs-iam"
 version = "1.0.0-rc.3"
@@ -10416,6 +10422,21 @@ dependencies = [
  "uuid",
 ]
 
+[[package]]
+name = "rustfs-scanner-contracts"
+version = "1.0.0-rc.3"
+dependencies = [
+ "chrono",
+ "jiff",
+ "metrics",
+ "rmp-serde",
+ "rustfs-heal-contracts",
+ "serde",
+ "serde_json",
+ "tokio",
+ "uuid",
+]
+
 [[package]]
 name = "rustfs-security-governance"
 version = "1.0.0-rc.3"