[Gradle] Rename experimental annotations to opt-in annotations in DSL

Methods and accessors with old names are preserved in public API and marked as deprecated now
#KT-38111 In Progress

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/LanguageSettingsBuilder.kt

@@ -18,7 +18,10 @@ interface LanguageSettingsBuilder : LanguageSettings {
 
     override val enabledLanguageFeatures: Set<String>
 
+    @Deprecated("Unsupported and will be removed in next major releases", replaceWith = ReplaceWith("optInAnnotation(name)"))
     fun useExperimentalAnnotation(name: String)
 
+    fun optInAnnotation(name: String)
+
     override val experimentalAnnotationsInUse: Set<String>
 }