[BUG] The rocketmq 4.9.6 still use 'free' to get system memory

[kizuna-lek]

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BUG REPORT

1. Please describe the issue you observed:

• What did you do (The steps to reproduce)?
  get Rocketmq 4.9.6 from docker hub: https://hub.docker.com/r/apache/rocketmq/tags?name=4.9.6

• What did you expect to see?
  In calculate_heap_sizes function, get system memory from cgroup or env

• What did you see instead?
  get system memory from 'free' cmd

[lfq1234]

The early versions of RocketMQ used the free command to get system memory because it was simple and direct. Although better methods exist, the development team has kept the current approach to ensure backward compatibility and avoid introducing new issues through code changes, which require rigorous testing and validation.