[FE 1.0] Postpone turning NON_VARARG_SPREAD_WARNING into error till 1.8 to have a deprecation cycle of proper duration

^KT-48162

compiler/testData/diagnostics/tests/collectionLiterals/collectionLiteralsWithVarargs.kt

@@ -33,7 +33,7 @@ fun test6() {}
 
 annotation class AnnArray(val a: Array<String>)
 
-@AnnArray(<!NON_VARARG_SPREAD_ERROR!>*<!>["/"])
+@AnnArray(<!NON_VARARG_SPREAD_WARNING!>*<!>["/"])
 fun testArray() {}
 
 @Ann1(<!TYPE_MISMATCH, TYPE_MISMATCH!>[""]<!>)

compiler/testData/diagnostics/tests/varargs/kt48162.kt

@@ -12,9 +12,9 @@ class Foo<T> {
 
 fun use(arg: Array<String>, s: Collection<String>, x: Foo<String>) {
     arr(<!NON_VARARG_SPREAD_ERROR!>*<!>arg)
-    arr(<!NON_VARARG_SPREAD_ERROR!>*<!>s.toArray())
+    arr(<!NON_VARARG_SPREAD_WARNING!>*<!>s.toArray())
     arr(<!NON_VARARG_SPREAD_ERROR!>*<!>s.toArray2())
-    arr(<!NON_VARARG_SPREAD_ERROR!>*<!>toArray3(s))
+    arr(<!NON_VARARG_SPREAD_WARNING!>*<!>toArray3(s))
     arr(<!NON_VARARG_SPREAD_ERROR!>*<!>x + x)
     arr(<!NON_VARARG_SPREAD_ERROR!>*<!>(x + x))
 }

compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -222,7 +222,6 @@ enum class LanguageFeature(
     ProhibitSmartcastsOnPropertyFromAlienBaseClass(KOTLIN_1_7, kind = BUG_FIX),
     ProhibitInvalidCharsInNativeIdentifiers(KOTLIN_1_7, kind = BUG_FIX),
     DefinitelyNonNullableTypes(KOTLIN_1_7),
-    ReportNonVarargSpreadOnGenericCalls(KOTLIN_1_7, kind = BUG_FIX),
     ProhibitSimplificationOfNonTrivialConstBooleanExpressions(KOTLIN_1_7),
     SafeCallsAreAlwaysNullable(KOTLIN_1_7),
     RefineTypeCheckingOnAssignmentsToJavaFields(KOTLIN_1_7),
@@ -262,6 +261,7 @@ enum class LanguageFeature(
     ModifierNonBuiltinSuspendFunError(KOTLIN_1_8),
     SynchronizedSuspendError(KOTLIN_1_8),
     EnableDfaWarningsInK2(KOTLIN_1_8, kind = OTHER), // KT-50965
+    ReportNonVarargSpreadOnGenericCalls(KOTLIN_1_8, kind = BUG_FIX), // KT-48162
 
     // 1.9