[Distributed] Runtime: Implement a way to access generic env of distributed target

stdlib/public/Distributed/DistributedMetadata.swift

@@ -78,3 +78,14 @@ func __getReturnTypeInfo(
     _ typeNameStart: UnsafePointer<UInt8>,
     _ typeNameLength: UInt
 ) -> Any.Type?
+
+
+/// Retrieve a generic environment descriptor associated with
+/// the given distributed target
+@available(SwiftStdlib 5.6, *)
+@_silgen_name("swift_distributed_get_generic_environment")
+public // SPI _Distributed
+func _getGenericEnvironmentOfDistributedTarget(
+    _ targetNameStart: UnsafePointer<UInt8>,
+    _ targetNameLength: UInt
+) -> UnsafeRawPointer?