refactor(ecstore): move HealOperations into set_disk::ops::heal (backlog#817) (#4267)

P1 of the SetDisks split (tracking backlog#815, depends on P0 backlog#816).

Give the Heal operation family its own module home: relocate set_disk/heal.rs
to set_disk/ops/heal.rs and move the HealOperations storage-api contract impl
beside its inherent helpers. The contract stays implemented for SetDisks so its
associated-type bounds are unchanged (ecstore_contract_compat_test still
covers it).

Method bodies are moved unchanged. The four inherent helpers widen from
pub(super) to pub(in crate::set_disk) to preserve their exact prior visibility
from the deeper module. get_pool_and_set now reads topology through
SetDisksCtx to keep the Heal family aligned with the P0 borrow pattern; the
read is provably identical (ctx.format()/pool_index() alias the core fields).

Runtime behavior is unchanged.

crates/ecstore/src/set_disk/ops/mod.rs

@@ -0,0 +1,20 @@
+// Copyright 2024 RustFS Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Home for the `SetDisks` operation families extracted during the
+//! God-Object split (tracking #815). Each family owns its module here and
+//! borrows shared state through [`super::ctx::SetDisksCtx`]; the storage-api
+//! contract impls stay `for SetDisks`, so contract bounds are unchanged.
+
+pub(crate) mod heal;