Tests: remove @testable import CoreCommands

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

Author: compnerd

Tests/BuildTests/PrepareForIndexTests.swift

@@ -13,7 +13,7 @@
 import Build
 import Foundation
 @testable import Commands
-@testable import CoreCommands
+import CoreCommands
 import LLBuildManifest
 import _InternalTestSupport
 import TSCBasic

Tests/CommandsTests/BuildCommandTests.swift

@@ -13,7 +13,7 @@
 import Foundation
 import Basics
 @testable import Commands
-@testable import CoreCommands
+import CoreCommands
 import PackageGraph
 import PackageLoading
 import PackageModel

Tests/CommandsTests/PackageCommandTests.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 import Basics
-@testable import CoreCommands
+import CoreCommands
 @testable import Commands
 import Foundation
 

Tests/CommandsTests/SwiftCommandStateTests.swift

@@ -13,7 +13,7 @@
 import Basics
 import Build
 @testable import Commands
-@testable import CoreCommands
+import CoreCommands
 
 @_spi(DontAdoptOutsideOfSwiftPMExposedForBenchmarksAndTestsOnly)
 import func PackageGraph.loadModulesGraph