Revert heal locks (#12365)

A lot of healing is likely to be on non-existing objects and 
locks are very expensive and will slow down scanning 
significantly.

In cases where all are valid or, all are broken allow 
rejection without locking.

Keep the existing behavior, but move the check for 
dangling objects to after the lock has been acquired.

```
	_, err = getLatestFileInfo(ctx, partsMetadata, errs)
	if err != nil {
		return er.purgeObjectDangling(ctx, bucket, object, versionID, partsMetadata, errs, []error{}, opts)
	}
```

Revert "heal: Hold lock when reading xl.meta from disks (#12362)"

This reverts commit abd32065aa

cmd/erasure-healing-common.go

@@ -189,6 +189,35 @@ func getLatestFileInfo(ctx context.Context, partsMetadata []FileInfo, errs []err
 	return latestFileInfo, nil
 }
 
+// fileInfoConsistent whether all fileinfos are consistent with each other.
+// Will return false if any fileinfo mismatches.
+func fileInfoConsistent(ctx context.Context, partsMetadata []FileInfo, errs []error) bool {
+	// There should be atleast half correct entries, if not return failure
+	if reducedErr := reduceReadQuorumErrs(ctx, errs, nil, len(partsMetadata)/2); reducedErr != nil {
+		return false
+	}
+	if len(partsMetadata) == 1 {
+		return true
+	}
+	// Reference
+	ref := partsMetadata[0]
+	if !ref.IsValid() {
+		return false
+	}
+	for _, meta := range partsMetadata[1:] {
+		if !meta.IsValid() {
+			return false
+		}
+		if !meta.ModTime.Equal(ref.ModTime) {
+			return false
+		}
+		if meta.DataDir != ref.DataDir {
+			return false
+		}
+	}
+	return true
+}
+
 // disksWithAllParts - This function needs to be called with
 // []StorageAPI returned by listOnlineDisks. Returns,
 //