## What changes were proposed in this pull request?
In `HeapMemoryAllocator`, when allocating memory from pool, and the key of pool is memory size.
Actually some size of memory ,such as 1025bytes,1026bytes,......1032bytes, we can think they are the same，because we allocate memory in multiples of 8 bytes.
In this case, we can improve memory reuse.
## How was this patch tested?
Existing tests and added unit tests
Author: liuxian <liu.xian3@zte.com.cn>
Closes#19077 from 10110346/headmemoptimize.
76e019d9bd