Use stdlib functions for currentTimeMillis and measureTimeMillis

mirai-core-utils/src/nativeMain/kotlin/Clock.kt

@@ -12,7 +12,5 @@
 package net.mamoe.mirai.utils
 
 public actual inline fun measureTimeMillis(block: () -> Unit): Long {
-    val start = currentTimeMillis()
-    block()
-    return currentTimeMillis() - start
+    return kotlin.system.measureTimeMillis(block)
 }

mirai-core-utils/src/nativeMain/kotlin/TimeUtils.kt

@@ -13,20 +13,16 @@ package net.mamoe.mirai.utils
 
 import kotlinx.cinterop.*
 import platform.posix.*
+import kotlin.system.getTimeMillis
 
 /**
  * 时间戳
- *
- * @see System.currentTimeMillis
  */
 public actual fun currentTimeMillis(): Long {
-    memScoped {
-        val timeT = alloc<time_tVar>()
-        time(timeT.ptr)
-        return timeT.value
-    }
+    return getTimeMillis()
 }
 
+@OptIn(UnsafeNumber::class)
 public actual fun currentTimeFormatted(format: String?): String {
     memScoped {
         val timeT = alloc<time_tVar>()