refactor(lib): Switch from pin-project to pin-project-lite (#2566)

Note the practical affects of this change:

- Dependency count with --features full dropped from 65 to 55.
- Time to compile after a clean dropped from 48s to 35s (on a pretty underpowered VM).

Closes #2388

Cargo.toml

@@ -34,7 +34,7 @@ httparse = "1.4"
 h2 = { version = "0.3.3", optional = true }
 itoa = "0.4.1"
 tracing = { version = "0.1", default-features = false, features = ["std"] }
-pin-project = "1.0"
+pin-project-lite = "0.2.4"
 tower-service = "0.3"
 tokio = { version = "1", features = ["sync"] }
 want = "0.3"