Stabilize Duration, DurationUnit and related top-level functions KT-46784

Co-authored-by: Abduqodiri Qurbonzoda <abduqodiri.qurbonzoda@jetbrains.com>

libraries/stdlib/jvm/src/kotlin/time/DurationUnitJvm.kt

@@ -8,12 +8,11 @@
 
 package kotlin.time
 
-@SinceKotlin("1.3")
-@ExperimentalTime
+@SinceKotlin("1.6")
+@WasExperimental(ExperimentalTime::class)
 public actual typealias DurationUnit = java.util.concurrent.TimeUnit
 
 @SinceKotlin("1.3")
-@ExperimentalTime
 internal actual fun convertDurationUnit(value: Double, sourceUnit: DurationUnit, targetUnit: DurationUnit): Double {
     val sourceInTargets = targetUnit.convert(1, sourceUnit)
     if (sourceInTargets > 0)
@@ -24,13 +23,11 @@ internal actual fun convertDurationUnit(value: Double, sourceUnit: DurationUnit,
 }
 
 @SinceKotlin("1.5")
-@ExperimentalTime
 internal actual fun convertDurationUnitOverflow(value: Long, sourceUnit: DurationUnit, targetUnit: DurationUnit): Long {
     return targetUnit.convert(value, sourceUnit)
 }
 
 @SinceKotlin("1.5")
-@ExperimentalTime
 internal actual fun convertDurationUnit(value: Long, sourceUnit: DurationUnit, targetUnit: DurationUnit): Long {
     return targetUnit.convert(value, sourceUnit)
 }