[ExplicitModuleBuild] Add a dependency scanning test for package interface

Add a test for dependency scanning for package interface to ensure the
correct interface is found when package interface is enabled.

Author: cachemeifyoucan

test/ScanDependencies/package_interface.swift

@@ -0,0 +1,30 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend -emit-module %t/Bar.swift -I %t \
+// RUN:   -module-name Bar -package-name barpkg \
+// RUN:   -enable-library-evolution -swift-version 5 \
+// RUN:   -emit-module-interface-path %t/Bar.swiftinterface \
+// RUN:   -emit-private-module-interface-path %t/Bar.private.swiftinterface \
+// RUN:   -emit-package-module-interface-path %t/Bar.package.swiftinterface
+
+// RUN: %target-swift-frontend -scan-dependencies -o %t/deps.json -I %t -experimental-package-interface-load \
+// RUN:   %t/Client.swift -module-name Client -package-name barpkg -swift-version 5
+
+// RUN: %FileCheck %s --input-file=%t/deps.json
+
+// CHECK: "swift": "Bar"
+// CHECK: "modulePath": "{{.*}}{{/|\\}}Bar-{{.*}}.swiftmodule"
+// CHECK: "moduleInterfacePath": "{{.*}}{{/|\\}}Bar.package.swiftinterface"
+
+//--- Bar.swift
+public enum PubEnum {
+  case red, green
+}
+
+package enum PkgEnum {
+  case blue, yellow
+}
+
+//--- Client.swift
+import Bar