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/benches/benchmark.rs

@@ -0,0 +1,61 @@
+use benchmark_simple::*;
+use coarsetime::*;
+use std::time;
+
+fn main() {
+    let options = &Options {
+        iterations: 250_000,
+        warmup_iterations: 25_000,
+        min_samples: 5,
+        max_samples: 10,
+        max_rsd: 1.0,
+        ..Default::default()
+    };
+    bench_coarsetime_now(options);
+    bench_coarsetime_recent(options);
+    bench_coarsetime_elapsed(options);
+    bench_coarsetime_elapsed_since_recent(options);
+    bench_stdlib_now(options);
+    bench_stdlib_elapsed(options);
+}
+
+fn bench_coarsetime_now(options: &Options) {
+    let b = Bench::new();
+    Instant::update();
+    let res = b.run(options, Instant::now);
+    println!("coarsetime_now():          {}", res.throughput(1));
+}
+
+fn bench_coarsetime_recent(options: &Options) {
+    let b = Bench::new();
+    Instant::update();
+    let res = b.run(options, Instant::recent);
+    println!("coarsetime_recent():       {}", res.throughput(1));
+}
+
+fn bench_coarsetime_elapsed(options: &Options) {
+    let b = Bench::new();
+    let ts = Instant::now();
+    let res = b.run(options, || ts.elapsed());
+    println!("coarsetime_elapsed():      {}", res.throughput(1));
+}
+
+fn bench_coarsetime_elapsed_since_recent(options: &Options) {
+    let b = Bench::new();
+    let ts = Instant::now();
+    let res = b.run(options, || ts.elapsed_since_recent());
+    println!("coarsetime_since_recent(): {}", res.throughput(1));
+}
+
+fn bench_stdlib_now(options: &Options) {
+    let b = Bench::new();
+    let res = b.run(options, time::Instant::now);
+    println!("stdlib_now():              {}", res.throughput(1));
+}
+
+fn bench_stdlib_elapsed(options: &Options) {
+    let b = Bench::new();
+    let ts = time::Instant::now();
+    let res = b.run(options, || ts.elapsed());
+    println!("stdlib_elapsed():          {}", res.throughput(1));
+}