feat: remove metric/memory package (#251)

## What does this PR do?

most of the feature are covered by go-sysinfo or existing system
libraries that we use

the package is not used by any supported project so just remove it

## Why is it important?

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## Checklist

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- [ ] My code follows the style guidelines of this project
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## Related issues

Blocked by elastic/beats#45157
Includes
#250 to
solve a compile error

Author: kruskall