Vendor dependencies

Let's see how I like this workflow.

vendor/parking_lot/Cargo.toml

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+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "parking_lot"
+version = "0.12.1"
+authors = ["Amanieu d'Antras <amanieu@gmail.com>"]
+description = "More compact and efficient implementations of the standard synchronization primitives."
+readme = "README.md"
+keywords = [
+    "mutex",
+    "condvar",
+    "rwlock",
+    "once",
+    "thread",
+]
+categories = ["concurrency"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/Amanieu/parking_lot"
+
+[dependencies.lock_api]
+version = "0.4.6"
+
+[dependencies.parking_lot_core]
+version = "0.9.0"
+
+[dev-dependencies.bincode]
+version = "1.3.3"
+
+[dev-dependencies.rand]
+version = "0.8.3"
+
+[features]
+arc_lock = ["lock_api/arc_lock"]
+deadlock_detection = ["parking_lot_core/deadlock_detection"]
+default = []
+hardware-lock-elision = []
+nightly = [
+    "parking_lot_core/nightly",
+    "lock_api/nightly",
+]
+owning_ref = ["lock_api/owning_ref"]
+send_guard = []
+serde = ["lock_api/serde"]