docs: document crypto RC version dependencies (#732) (#4011)

* docs: document crypto RC version dependencies

Add comment explaining why aes-gcm and chacha20poly1305 use RC
versions and the migration path when stable versions are released.

Refs #732

* fix: remove all backlog links from code and comments

crates/config/src/constants/zero_copy.rs

@@ -17,7 +17,6 @@
 //! This module defines environment variables and default values for mmap-based
 //! read operations. Note: despite the "zero_copy" naming in env vars (kept for
 //! backward compatibility), the actual implementation performs mmap-then-copy,
-//! not true zero-copy. See https://github.com/rustfs/backlog/issues/733
 
 // =============================================================================
 // Mmap Read Configuration

crates/io-core/Cargo.toml

@@ -36,7 +36,6 @@ rustfs-io-metrics = { workspace = true }
 
 # Enable tokio's io_uring-based runtime backend on Linux.
 # Note: this is a tokio runtime feature, not application-level io_uring usage.
-# See https://github.com/rustfs/backlog/issues/733
 [target.'cfg(target_os = "linux")'.dependencies]
 tokio = { workspace = true, features = ["io-uring"] }
 

crates/io-core/src/lib.rs

@@ -17,7 +17,6 @@
 //! This crate provides buffered readers and writers for I/O operations.
 //! Note: despite "ZeroCopy" naming in type names (kept for backward compatibility),
 //! the actual implementations perform mmap-then-copy or aligned pread, not true
-//! zero-copy. See https://github.com/rustfs/backlog/issues/733
 //!
 //! # Features
 //!