Tests: remove @testable import PackageRegistry

Use the newly extended APIs for testing and use a non-testable import of
the package, avoiding a recompilation.

Author: compnerd

Tests/PackageRegistryTests/PackageSigningEntityTOFUTests.swift

@@ -14,7 +14,7 @@ import Foundation
 
 import Basics
 import PackageModel
-@testable import PackageRegistry
+import PackageRegistry
 import PackageSigning
 import _InternalTestSupport
 import XCTest

Tests/PackageRegistryTests/PackageVersionChecksumTOFUTests.swift

@@ -15,7 +15,7 @@ import _Concurrency
 import Foundation
 import PackageFingerprint
 import PackageModel
-@testable import PackageRegistry
+import PackageRegistry
 import _InternalTestSupport
 import XCTest
 

Tests/PackageRegistryTests/RegistryClientTests.swift

@@ -16,7 +16,7 @@ import Foundation
 import PackageFingerprint
 import PackageLoading
 import PackageModel
-@testable import PackageRegistry
+import PackageRegistry
 import PackageSigning
 import _InternalTestSupport
 import Testing

Tests/PackageRegistryTests/RegistryDownloadsManagerTests.swift

@@ -14,7 +14,7 @@ import Basics
 import _Concurrency
 import PackageModel
 import PackageLoading
-@testable import PackageRegistry
+import PackageRegistry
 import _InternalTestSupport
 import XCTest
 

Tests/PackageRegistryTests/SignatureValidationTests.swift

@@ -13,7 +13,7 @@
 import Basics
 import Foundation
 import PackageModel
-@testable import PackageRegistry
+import PackageRegistry
 import PackageSigning
 import _InternalTestSupport
 import X509 // FIXME: need this import or else SwiftSigningIdentity init crashes