add docker compose setup for swift 5.8

motivation: prepare for swift 5.8

changes:
* update docker compose setup to use release version of 5.7
* add docker compose setup for nightly 5.8

Author: tomerd

docker/docker-compose.2004.57.yaml

@@ -6,7 +6,8 @@ services:
     image: swift-service-lifecycle:20.04-5.7
     build:
       args:
-        base_image: "swiftlang/swift:nightly-main-focal"
+        ubuntu_version: "focal"
+        swift_version: "5.7"
 
   test:
     image: swift-service-lifecycle:20.04-5.7

docker/docker-compose.2004.58.yaml

@@ -0,0 +1,18 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-service-lifecycle:20.04-5.8
+    build:
+      args:
+        base_image: "swiftlang/swift:nightly-5.8-focal"
+
+  test:
+    image: swift-service-lifecycle:20.04-5.8
+    environment:
+      - SKIP_SIGNAL_TEST=true
+      - FORCE_TEST_DISCOVERY=--enable-test-discovery
+
+  shell:
+    image: swift-service-lifecycle:20.04-5.8