[platform] Refactor current_memory_usage() function in DeviceMemoryProfiler into Platform

[shen-shanshan]

What does this PR do?

This PR is a refactoring of current_memory_usage() function in DeviceMemoryProfiler.

I put this function into Platform and implement it in each XxxPlatform subclass, making DeviceMemoryProfiler platform agnostic.

[github-actions]

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