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>

rustfs/Cargo.toml

@@ -191,8 +191,6 @@ mimalloc = { workspace = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]
 libsystemd.workspace = true
-# io-uring is Linux-only. Scope the feature to Linux targets.
-tokio = { workspace = true, features = ["io-uring"] }
 
 [target.'cfg(not(target_os = "windows"))'.dependencies]
 libmimalloc-sys = { version = "0.1.49", features = ["extended"] }