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/.cargo_vcs_info.json

@@ -0,0 +1,6 @@
+{
+  "git": {
+    "sha1": "831c97016aa3d8f7851999aa1deea8407e7cbd42"
+  },
+  "path_in_vcs": ""
+}