Duration: do not use scientific format for large values

The largest duration value formatted in ns with maximal decimals
would fit in 40 chars.

kotlin-native/runtime/src/main/cpp/ToString.cpp

@@ -108,15 +108,10 @@ OBJ_GETTER(Kotlin_Long_toStringRadix, KLong value, KInt radix) {
 }
 
 OBJ_GETTER(Kotlin_DurationValue_formatToExactDecimals, KDouble value, KInt decimals) {
-  char cstring[32];
+  char cstring[40]; // log(2^62*1_000_000) + 2 (sign, decimal point) + 12 (max decimals)
   konan::snprintf(cstring, sizeof(cstring), "%.*f", decimals, value);
   RETURN_RESULT_OF(CreateStringFromCString, cstring)
 }
 
-OBJ_GETTER(Kotlin_DurationValue_formatScientificImpl, KDouble value) {
-  char cstring[16];
-  konan::snprintf(cstring, sizeof(cstring), "%.2e", value);
-  RETURN_RESULT_OF(CreateStringFromCString, cstring)
-}
 
 } // extern "C"

kotlin-native/runtime/src/main/kotlin/kotlin/time/formatToDecimals.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 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.
  */
 
@@ -13,12 +13,3 @@ internal actual external fun formatToExactDecimals(value: Double, decimals: Int)
 internal actual fun formatUpToDecimals(value: Double, decimals: Int): String {
     return formatToExactDecimals(value, decimals).trimEnd('0')
 }
-
-@GCUnsafeCall("Kotlin_DurationValue_formatScientificImpl")
-internal external fun formatScientificImpl(value: Double): String
-
-internal actual fun formatScientific(value: Double): String {
-    val result = formatScientificImpl(value)
-    val expIndex = result.indexOf("e+0")
-    return if (expIndex < 0) result else result.removeRange(expIndex + 2, expIndex + 3)
-}