fix(runtime): remove tokio io-uring feature and add regression guard (#4364)

Drop the [target.'cfg(target_os = "linux")'.dependencies] tokio
"io-uring" feature from 6 crates and the rustfs binary. Because
.cargo/config.toml enables --cfg tokio_unstable globally, this feature
switched every Linux build's file I/O onto tokio's io_uring runtime
backend. Restricted Linux environments (Docker default seccomp, gVisor,
proot, old kernels) reject io_uring_setup with EACCES/ENOSYS, which
tokio surfaced as PermissionDenied and RustFS reported as
DiskAccessDenied at startup.

Add scripts/check_no_tokio_io_uring.sh so the feature cannot silently
return: it fails on any tokio dependency line enabling "io-uring", while
still allowing a future application-level io-uring crate dependency.
Wire it into make pre-commit/pre-pr/dev-check and CI.

Tracking: rustfs/backlog#890 (parent rustfs/backlog#897)

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

scripts/check_no_tokio_io_uring.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Guard: tokio's io-uring runtime backend must stay disabled.
+#
+# Restricted Linux environments (Docker default seccomp, gVisor, proot,
+# old kernels) reject io_uring_setup with EACCES/ENOSYS. With the global
+# `--cfg tokio_unstable` in .cargo/config.toml, a tokio "io-uring" feature
+# anywhere in the workspace silently switches every Linux build's file I/O
+# onto that backend and turns the rejection into DiskAccessDenied at
+# startup (backlog#890). Any future io_uring integration must go through
+# an application-level, runtime-probed backend (backlog#894), never the
+# tokio runtime feature — so only the tokio dependency line is banned
+# here; an explicit `io-uring` crate dependency is allowed.
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT_DIR="${CHECK_NO_TOKIO_IO_URING_ROOT:-$(cd "${SCRIPT_DIR}/.." && pwd)}"
+
+cd "$ROOT_DIR"
+
+status=0
+
+while IFS=: read -r file line content; do
+    printf '%s:%s: tokio must not enable the "io-uring" runtime feature: %s\n' \
+        "$file" "$line" "$content" >&2
+    status=1
+done < <(rg -n '^[[:space:]]*tokio[[:space:]]*=.*"io-uring"' --glob '**/Cargo.toml' . || true)
+
+exit "$status"