[FIR, IR] Refactor: move annotation retention helper functions

Will be needed in subsequent commit to be accessible in
ExpectActualMatchingContext implementations.

^KT-58551

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/analysis/FirRetentionAnnotationHelpers.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.analysis
+
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.declarations.FirDeclaration
+import org.jetbrains.kotlin.fir.declarations.FirRegularClass
+import org.jetbrains.kotlin.fir.declarations.findArgumentByName
+import org.jetbrains.kotlin.fir.declarations.getAnnotationByClassId
+import org.jetbrains.kotlin.fir.expressions.FirAnnotation
+import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
+import org.jetbrains.kotlin.fir.references.toResolvedEnumEntrySymbol
+import org.jetbrains.kotlin.name.StandardClassIds
+
+fun FirRegularClass.getRetention(session: FirSession): AnnotationRetention {
+    return getRetentionAnnotation(session)?.getRetention() ?: AnnotationRetention.RUNTIME
+}
+
+fun FirAnnotation.getRetention(): AnnotationRetention? {
+    val propertyAccess = findArgumentByName(StandardClassIds.Annotations.ParameterNames.retentionValue) as? FirQualifiedAccessExpression
+    val callableId = propertyAccess?.calleeReference?.toResolvedEnumEntrySymbol()?.callableId ?: return null
+
+    if (callableId.classId != StandardClassIds.AnnotationRetention) {
+        return null
+    }
+
+    return AnnotationRetention.entries.firstOrNull { it.name == callableId.callableName.asString() }
+}
+
+fun FirDeclaration.getRetentionAnnotation(session: FirSession): FirAnnotation? {
+    return getAnnotationByClassId(StandardClassIds.Annotations.Retention, session)
+}