Remove all code that soly existed to support Swift 5.8

Author: fabianfett

Diff for: Sources/ConnectionPoolModule/ConnectionPool.swift

@@ -571,20 +571,6 @@ extension PoolConfiguration {
     }
 }
 
-#if swift(<5.9)
-// This should be removed once we support Swift 5.9+ only
-extension AsyncStream {
-    static func makeStream(
-        of elementType: Element.Type = Element.self,
-        bufferingPolicy limit: Continuation.BufferingPolicy = .unbounded
-    ) -> (stream: AsyncStream<Element>, continuation: AsyncStream<Element>.Continuation) {
-        var continuation: AsyncStream<Element>.Continuation!
-        let stream = AsyncStream<Element>(bufferingPolicy: limit) { continuation = $0 }
-        return (stream: stream, continuation: continuation!)
-    }
-}
-#endif
-
 @usableFromInline
 protocol TaskGroupProtocol {
     // We need to call this `addTask_` because some Swift versions define this

Diff for: Sources/PostgresNIO/New/NotificationListener.swift

@@ -140,19 +140,3 @@ final class NotificationListener: @unchecked Sendable {
         }
     }
 }
-
-
-#if compiler(<5.9)
-// Async stream API backfill
-extension AsyncThrowingStream {
-    static func makeStream(
-         of elementType: Element.Type = Element.self,
-         throwing failureType: Failure.Type = Failure.self,
-         bufferingPolicy limit: Continuation.BufferingPolicy = .unbounded
-     ) -> (stream: AsyncThrowingStream<Element, Failure>, continuation: AsyncThrowingStream<Element, Failure>.Continuation) where Failure == Error {
-         var continuation: AsyncThrowingStream<Element, Failure>.Continuation!
-         let stream = AsyncThrowingStream<Element, Failure>(bufferingPolicy: limit) { continuation = $0 }
-         return (stream: stream, continuation: continuation!)
-     }
- }
- #endif