perf!: replace default engine JSON reader's FileStream with concurrent futures

feature-tests/src/lib.rs

@@ -1,7 +1,10 @@
 /// This is a compilation test to ensure that the default-engine feature flags are working
-/// correctly. Run (from workspace root) with:
+/// correctly.
+///
+/// Run (from workspace root) with:
 /// 1. `cargo b -p feature_tests --features default-engine-rustls`
 /// 2. `cargo b -p feature_tests --features default-engine`
+///
 /// These run in our build CI.
 pub fn test_default_engine_feature_flags() {
     #[cfg(any(feature = "default-engine", feature = "default-engine-rustls"))]

kernel/Cargo.toml

@@ -150,6 +150,7 @@ rustc_version = "0.4.1"
 [dev-dependencies]
 delta_kernel = { path = ".", features = ["arrow", "default-engine", "sync-engine"] }
 test_utils = { path = "../test-utils" }
+async-trait = "0.1" # only used for our custom SlowGetStore ObjectStore implementation
 paste = "1.0"
 test-log = { version = "0.2", default-features = false, features = ["trace"] }
 tempfile = "3"