KT-45777: Add debug log messages for classpath snapshot feature

Also clean up classpath snapshot shrinking a bit to make it clearer.

^KT-45777 In Progress

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/transforms/ClasspathEntrySnapshotTransform.kt

@@ -95,8 +95,11 @@ abstract class ClasspathEntrySnapshotTransform : TransformAction<ClasspathEntryS
             metrics.addMetric(BuildPerformanceMetric.CLASSPATH_ENTRY_SNAPSHOT_TRANSFORM_EXECUTION_COUNT, 1)
             if (classpathEntryInputDirOrJar.extension.equals("jar", ignoreCase = true)) {
                 metrics.addMetric(BuildPerformanceMetric.JAR_CLASSPATH_ENTRY_SIZE, classpathEntryInputDirOrJar.length())
+                metrics.addMetric(BuildPerformanceMetric.JAR_CLASSPATH_ENTRY_SNAPSHOT_SIZE, snapshotOutputFile.length())
+            } else {
+                // Only compute the size of the snapshot, not the size of the input directory as walking the file tree has a small overhead
+                metrics.addMetric(BuildPerformanceMetric.DIRECTORY_CLASSPATH_ENTRY_SNAPSHOT_SIZE, snapshotOutputFile.length())
             }
-            metrics.addMetric(BuildPerformanceMetric.CLASSPATH_ENTRY_SNAPSHOT_SIZE, snapshotOutputFile.length())
         }
     }
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/Tasks.kt

@@ -292,7 +292,7 @@ abstract class AbstractKotlinCompile<T : CommonCompilerArguments> @Inject constr
         private fun getKotlinBuildDir(task: T): Provider<Directory> =
             task.project.layout.buildDirectory.dir("$KOTLIN_BUILD_DIR_NAME/${task.name}")
 
-        protected fun getClasspathSnapshotDir(task: T): Provider<Directory> =
+        protected open fun getClasspathSnapshotDir(task: T): Provider<Directory> =
             getKotlinBuildDir(task).map { it.dir("classpath-snapshot") }
     }