perf: shared target dir, --no-deps for docs, parallel test execution

- Use ~/.facet-dev/target as shared target dir across worktrees
- Show target dir path and size at start of pre-push
- Add --no-deps to cargo doc for faster doc builds
- Separate test build from test run
- Run tests in background while clippy/docs/etc run
- Add dirs crate for home directory detection

Author: fasterthanlime

Cargo.lock

@@ -16,6 +16,7 @@ rustdoc-args = ["--html-in-header", "arborium-header.html"]
 
 [dependencies]
 cargo_metadata = "0.23.1"
+dirs = "6"
 fs-err = "3.2.0"
 log = { version = "0.4.29", features = ["std"] }
 owo-colors = "4.2.3"