bootstat: Refactor init/utils/boot_clock into base/chrono_utils.

Use this for bootstat and init. This replaces the custom uptime parser in
bootstat.

This is a reland of aosp/338325 with a stubbed implementation for Darwin.

This change also has clang_format fixes (automatic).

Bug: 34352037
Test: chrono_utils_test
Change-Id: I72a62a3ca1ccfc0a4ccc6294ff1776c263144686
diff --git a/init/init.cpp b/init/init.cpp
index 6f3b3a6..e14034f 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -40,6 +40,7 @@
 #include <selinux/label.h>
 #include <selinux/android.h>
 
+#include <android-base/chrono_utils.h>
 #include <android-base/file.h>
 #include <android-base/properties.h>
 #include <android-base/stringprintf.h>
@@ -69,6 +70,7 @@
 #include "util.h"
 #include "watchdogd.h"
 
+using android::base::boot_clock;
 using android::base::GetProperty;
 using android::base::StringPrintf;