Start a rust-based foreign document test.

Instead of using a simple bash script, this will use async rust to run multiple tests in parallel.

Cargo.toml

@@ -31,6 +31,12 @@ path = "src/lib.rs"
   path = "src/bin_compare.rs"
   required-features = ["compare"]
 
+[[bin]]
+  # This bin exists for development purposes only. The real target of this crate is the library.
+  name = "foreign_document_test"
+  path = "src/bin_foreign_document_test.rs"
+  required-features = ["foreign_document_test"]
+
 [dependencies]
 nom = "7.1.1"
 opentelemetry = { version = "0.20.0", optional = true, default-features = false, features = ["trace", "rt-tokio"] }
@@ -47,6 +53,7 @@ walkdir = "2.3.3"
 [features]
 default = []
 compare = []
+foreign_document_test = ["compare", "dep:tokio"]
 tracing = ["dep:opentelemetry", "dep:opentelemetry-otlp", "dep:opentelemetry-semantic-conventions", "dep:tokio", "dep:tracing", "dep:tracing-opentelemetry", "dep:tracing-subscriber"]
 
 # Optimized build for any sort of release.