3ad3356892
Motivation: PR [#6460] added a way to access the used memory of an allocator. The used naming was not very good and how things were exposed are not consistent. Modifications: - Add a new ByteBufAllocatorMetric and ByteBufAllocatorMetricProvider interface - Let the ByteBufAllocator implementations implement ByteBufAllocatorMetricProvider - Move exposed stats / metric from PooledByteBufAllocator to PooledByteBufAllocatorMetric and mark old methods as `@Deprecated`. Result: More consistent way to expose metric / stats for ByteBufAllocator