Adopt new PIF builder in SwiftBuildSupport (#8454)

### Motivation:

Switch from the legacy PIF builder in `SwiftBuildSupport` to 
the new one, introduced by PR #8405.

The new PIF builder (i.e., `SwiftBuildSupport/PackagePIFBuilder*.swift`)
is the exact same we use in Xcode.

### Modifications:

Replaces the old PIF builder (i.e., `SwiftBuildSupport/PIF.swift` 
and `SwiftBuildSupport/PIFBuilder.swift` ) with the new one 
(i.e., `SwiftBuildSupport/PackagePIFBuilder*.swift`).

### Result:

The new PIF builder now fully replaces the legacy PIF builder.

In particular, all these Swift Build tests are passing (i.e., same as before this PR):

* BuildPlanSwiftBuildTests
* APIDiffSwiftBuildTests
* BuildCommandSwiftBuildTests
* PackageCommandSwiftBuildTests
* RunCommandSwiftBuildTests
* TestCommandSwiftBuildTests

I also improved the PIF logging too. Try the `--very-verbose` option to see what I mean :-)

Tracked by rdar://147527170.

Author: pmattos

IntegrationTests/Tests/IntegrationTests/SwiftPMTests.swift

@@ -75,10 +75,15 @@ private struct SwiftPMTests {
     }
 
     @Test(
+        .requireHostOS(.windows, when: false),
         .requireThreadSafeWorkingDirectory,
         .bug(
             "https://github.com/swiftlang/swift-package-manager/issues/8416",
-            "swift run using --build-system swiftbuild fails to run executable"
+            "[Linux] swift run using --build-system swiftbuild fails to run executable"
+        ),
+        .bug(
+            "https://github.com/swiftlang/swift-package-manager/issues/8514",
+            "[Windows] Integration test SwiftPMTests.packageInitExecutable with --build-system swiftbuild is skipped"
         ),
         arguments: BuildSystemProvider.allCases
     )
@@ -119,12 +124,12 @@ private struct SwiftPMTests {
             try localFileSystem.createDirectory(packagePath)
             try sh(swiftPackage, "--package-path", packagePath, "init", "--type", "library")
             try withKnownIssue(
-                    """
-                    Linux: /lib/x86_64-linux-gnu/Scrt1.o:function _start: error: undefined reference to 'main'
-                    Windows: lld-link: error: subsystem must be defined
-                    MacOS: Could not find or use auto-linked library 'Testing': library 'Testing' not found
-                    """,
-                    isIntermittent: true
+                """
+                Linux: /lib/x86_64-linux-gnu/Scrt1.o:function _start: error: undefined reference to 'main'
+                Windows: lld-link: error: subsystem must be defined
+                MacOS: Could not find or use auto-linked library 'Testing': library 'Testing' not found
+                """,
+                isIntermittent: true
             ) {
                 try sh(swiftBuild, "--package-path", packagePath, "--build-system", buildSystemProvider.rawValue, "--vv")
                 let (stdout, stderr) = try sh(

Sources/SwiftBuildSupport/BuildSystem.swift

@@ -14,7 +14,7 @@ extension BuildSubset {
     var pifTargetName: String {
         switch self {
         case .product(let name, _):
-            _PackagePIFProjectBuilder.targetName(for: name)
+            targetName(forProductName: name)
         case .target(let name, _):
             name
         case .allExcludingTests: