arc: Fix the string_view dangling pointer issue

This CL create a new string when binding callback.

BUG=b:310260986
TEST=ArcAppLaunchThrottleObserverTest

Change-Id: I69074b817323b28baf1648e7296296a5a853bc77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5019669
Commit-Queue: Shengsong Tan <sstan@chromium.org>
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Reviewed-by: Alexandre Marciano Gimenez <raging@google.com>
Cr-Commit-Position: refs/heads/main@{#1224042}