Add MetricsTestUtils target (#11)

* Add MetricsTestUtils target

* code review

* Code format

* Fix CI for 5.0 and 5.1

* Returns for 5.0

Co-authored-by: Konrad `ktoso` Malawski <[email protected]>

Author: fabianfett

Package.swift

@@ -19,6 +19,7 @@ let package = Package(
     name: "swift-metrics-extras",
     products: [
         .library(name: "SystemMetrics", targets: ["SystemMetrics"]),
+        .library(name: "MetricsTestUtils", targets: ["MetricsTestUtils"]),
     ],
     dependencies: [
         .package(url: "https://github.com/apple/swift-metrics.git", from: "2.1.1"),
@@ -28,6 +29,10 @@ let package = Package(
             name: "SystemMetrics",
             dependencies: ["CoreMetrics"]
         ),
+        .target(
+            name: "MetricsTestUtils",
+            dependencies: ["Metrics", "CoreMetrics"]
+        ),
         .testTarget(
             name: "SystemMetricsTests",
             dependencies: ["SystemMetrics"]