[scudo] Fix the misused Exhausted in region allocation (#89852)

`Region->Exhausted` indicates that we don't have more pages to create
new blocks in the region. It has different meaning from region
allocation failure.

Also fix a minor lint in popBlocks()

Author: ChiaHungDuan

compiler-rt/lib/scudo/standalone/primary64.h

@@ -884,9 +884,10 @@ template <typename Config> class SizeClassAllocator64 {
         ScopedLock ML(Region->MMLock);
 
         const bool RegionIsExhausted = Region->Exhausted;
-        if (!RegionIsExhausted)
+        if (!RegionIsExhausted) {
           PopCount = populateFreeListAndPopBlocks(C, ClassId, Region, ToArray,
                                                   MaxBlockCount);
+        }
         ReportRegionExhausted = !RegionIsExhausted && Region->Exhausted;
 
         {
@@ -1019,7 +1020,6 @@ template <typename Config> class SizeClassAllocator64 {
                                           MAP_ALLOWNOMEM))) {
         Printf("Can't reserve pages for size class %zu.\n",
                getSizeByClassId(ClassId));
-        Region->Exhausted = true;
         return 0U;
       }
       initRegion(Region, ClassId,