perf(get): slim metadata fanout allocations (#1803) (#5968)

Every GET fans out a `read_version` across all disks to resolve xl.meta. Each
fanout allocated an `Arc<ReadOptions>` (3 bools) plus four `Arc<String>`
(`Arc::new(x.to_string())` = two allocations each) and cloned them into every
spawned task. This trims the per-fanout allocation footprint.

- `ReadOptions` is three bools, so it is now `Copy`. The fanout drops the
  `Arc<ReadOptions>` and hands each spawned task a copy; the two pre-existing
  `ReadOptions::clone()` sites (set_disk/read.rs, set_disk/ops/heal.rs) stop
  cloning a `Copy` type.
- The four request strings use `Arc::<str>::from(&str)` (one allocation each)
  instead of `Arc::new(..to_string())` (string buffer + Arc = two each) — four
  fewer allocations per fanout, transparent to the `read_version(&str)` call.

Behavior is unchanged: the fanout still spawns one task per disk (the spawn is
deliberate — `read_version_call_counter_observes_spawned_fanout` verifies the
process-global counter observes every per-disk increment across workers), quorum
/ early-stop / full-wait semantics are untouched, and no result ordering or
error handling changed.

Two larger items from the audit are intentionally NOT in this PR:
- `tokio::spawn` -> `FuturesUnordered`: the spawn is a tested, deliberate
  design (cross-worker counter observation for #1309/#1314), and converting
  would also change panic isolation. Left as-is.
- `vec![FileInfo::default(); N]`: `FileInfo`'s empty containers (String /
  HashMap / Vec) do not allocate, so this is one `Vec` allocation, not the
  per-element allocation the audit implied — not a real hot spot.

`cargo fmt`, `cargo clippy -p rustfs-ecstore --lib` (0 warnings),
`cargo check --lib --tests`, and the 26 fanout / call-counter unit tests pass
on macOS (the change is fully cross-platform).

Co-authored-by: heihutu <heihutu@gmail.com>
Co-authored-by: zhi22915 <qiuzgang@gmail.com>

crates/ecstore/src/disk/mod.rs

@@ -1251,7 +1251,7 @@ pub struct VolumeInfo {
     pub created: Option<OffsetDateTime>,
 }
 
-#[derive(Deserialize, Serialize, Debug, Default, Clone)]
+#[derive(Deserialize, Serialize, Debug, Default, Clone, Copy)]
 pub struct ReadOptions {
     pub incl_free_versions: bool,
     pub read_data: bool,