V8: Replace forLoop for forLoop reverse in getHeapSpaceStatistics

Replace forLoop for forLoop reverse, pre-decrement to improve the performance.

After running V8 benchmark this is the result:

With the actual for loop:

v8/get-stats.js
v8/get-stats.js n=1000000 method="getHeapStatistics": 3,925,281.1737783994
v8/get-stats.js n=1000000 method="getHeapSpaceStatistics": 3,079,267.8209353415

With for loop, reverse, pre-decrement:

v8/get-stats.js
v8/get-stats.js n=1000000 method="getHeapStatistics": 3,414,352.1774798837
v8/get-stats.js n=1000000 method="getHeapSpaceStatistics": 2,875,818.4633268225

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

V8