FIR: annotate 'replaceSource' with '@FirImplementationDetail'

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/element.kt

@@ -89,6 +89,9 @@ fun SmartPrinter.printElement(element: Element) {
 
             fun Field.replaceDeclaration(override: Boolean, overridenType: Importable? = null, forceNullable: Boolean = false) {
                 println()
+                if (name == "source") {
+                    println("@FirImplementationDetail")
+                }
                 abstract()
                 if (override) print("override ")
                 println(replaceFunctionDeclaration(overridenType, forceNullable))

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/implementation.kt

@@ -313,6 +313,9 @@ fun SmartPrinter.printImplementation(implementation: Implementation) {
                 body: () -> Unit,
             ) {
                 println()
+                if (field.name == "source") {
+                    println("@FirImplementationDetail")
+                }
                 abstract()
                 print("override ${field.replaceFunctionDeclaration(overridenType, forceNullable)}")
                 if (isInterface || isAbstract) {

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/utils.kt

@@ -10,7 +10,6 @@ import org.jetbrains.kotlin.fir.tree.generator.context.AbstractFirTreeBuilder
 import org.jetbrains.kotlin.fir.tree.generator.firImplementationDetailType
 import org.jetbrains.kotlin.fir.tree.generator.model.*
 import org.jetbrains.kotlin.fir.tree.generator.pureAbstractElementType
-import org.jetbrains.kotlin.utils.addToStdlib.runIf
 import java.io.File
 
 class GeneratedFile(val file: File, val newText: String)
@@ -71,7 +70,11 @@ private fun Element.collectImportsInternal(base: List<String>, kind: ImportKind)
             allFields.flatMap { it.overridenTypes.mapNotNull { it.fullQualifiedName } } +
             allFields.flatMap { it.arguments.mapNotNull { it.fullQualifiedName } } +
             typeArguments.flatMap { it.upperBounds.mapNotNull { it.fullQualifiedName } }
-    return fqns.filterRedundantImports(packageName, kind)
+    val result = fqns.filterRedundantImports(packageName, kind)
+    if (allFields.any { it.name == "source" && it.withReplace }) {
+        return (result + "org.jetbrains.kotlin.fir.FirImplementationDetail").distinct()
+    }
+    return result
 }
 
 private fun List<String>.filterRedundantImports(