fix: Patch coarsetime for MIPS AtomicU64 support

- Vendor coarsetime crate with portable-atomic fallback
- Use portable-atomic on targets without 64-bit atomics
- Patch crates.io to use local coarsetime
- Fixes MIPS build failure (AtomicU64 missing)

third_party/coarsetime/src/lib.rs

@@ -0,0 +1,37 @@
+//! A crate to make time measurements that focuses on speed.
+//!
+//! This crate is a partial replacement for the `Time` and `Duration` structures
+//! from the standard library, with the following differences:
+//!
+//! * Speed is privileged over accuracy. In particular, `CLOCK_MONOTONIC_COARSE`
+//!   is used to retrieve the clock value on Linux systems, and transformations avoid
+//!   operations that can be slow on non-Intel systems.
+//! * The number of system calls can be kept to a minimum. The "most recent
+//!   timestamp" is always kept in memory.
+//!   It can be read with just a load operation, and can be
+//!   updated only as frequently as necessary.
+//!
+//! # Installation
+//!
+//! `coarsetime` is available on [crates.io](https://crates.io/crates/coarsetime) and works on
+//! Rust stable, beta, and nightly.
+//!
+//! Windows and Unix-like systems are supported.
+
+#![allow(clippy::trivially_copy_pass_by_ref)]
+
+mod clock;
+mod duration;
+mod helpers;
+mod instant;
+#[cfg(not(any(target_arch = "wasm32", target_arch = "wasm64")))]
+mod updater;
+
+#[cfg(test)]
+mod tests;
+
+pub use self::clock::*;
+pub use self::duration::*;
+pub use self::instant::*;
+#[cfg(not(any(target_arch = "wasm32", target_arch = "wasm64")))]
+pub use self::updater::*;