chore(redux): prefer core/alloc over std

[0xDevNinja]

Description

First incremental step toward #1260. Scope is the reusable libs/redux crate only — swap std::X for core::X / alloc::X wherever an equivalent exists, and add extern crate alloc; at the crate root.

Changes (8 files, +20/-17):

• lib.rs — add extern crate alloc;
• dispatcher.rs — std::collections::VecDeque → alloc::collections::VecDeque; std::marker::PhantomData → core::marker::PhantomData
• callback.rs — std::borrow::Cow → alloc::borrow::Cow; std::any::{Any,type_name} → core::any::{Any,type_name} (incl. inside the public _callback! macro body)
• timestamp.rs, action/action_id.rs, action/action_with_meta.rs, action/action_meta.rs — std::time::Duration → core::time::Duration; impl std::ops::Add → impl core::ops::Add (3 impls)
• instant.rs — std::{cell::RefCell, cmp, ops, time::Duration} → core::{...}; std::fmt::{Debug,Formatter,Result} → core::fmt::{...}

Left on std:: (no core/alloc equivalent):

• std::sync::OnceLock in store.rs — needs platform sync primitives
• std::time::Instant, std::time::SystemTime — not in core; existing wasm-timer shim already covers cfg(target_arch = "wasm32")
• thread_local! macro in instant.rs — std-only macro

No behaviour change.

Related Issue(s)

Refs #1260.

Intentionally not a Closes — #1260 spans the whole workspace. This PR lands the leaf library first to validate the direction; further crates (crates/core, crates/p2p, crates/node, crates/ledger, …) follow in separate PRs.

Type of Change

• Refactoring (no functional changes)

Testing

Local, branched off fresh upstream/develop:

cargo check -p redux
cargo clippy -p redux --all-targets --no-deps -- --deny=warnings
cargo test -p redux
cargo check --workspace
cargo fmt --all --check
make check-trailing-whitespace

All green. cargo check --workspace produces only pre-existing warnings in crates/node and crates/p2p unrelated to this diff.

Changelog Entry

Changelog Summary: Changed the redux library to prefer core:: and alloc:: paths over std:: where possible (refs #1260).