refactor: use sysinfo for FreeBSD memory and process data extraction

[ClementTsang]

Description

A description of the change, what it does, and why it was made. If relevant (such as any change that modifies the UI), please provide screenshots of the changes:

I noticed that we can avoid custom data collection code for some parts of FreeBSD since sysinfo should support it.

Issue

If applicable, what issue does this address?

Closes: #

Testing

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If this is a code change, please also indicate which platforms were tested:

• [ ] Windows
• [ ] macOS
• [ ] Linux

Checklist

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• [ ] Areas your change affects have been linted using rustfmt (cargo fmt)
• [ ] The change has been tested and doesn't appear to cause any unintended breakage
• [ ] Documentation has been added/updated if needed (README.md, help menu, doc pages, etc.)
• [ ] The pull request passes the provided CI pipeline
• [ ] There are no merge conflicts
• [ ] If relevant, new tests were added (don't worry too much about coverage)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 54.87%. Comparing base (ee2e1fe) to head (a4ab82b).

:exclamation: Current head a4ab82b differs from pull request most recent head 4648d60

Please upload reports for the commit 4648d60 to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1474 +/- ## =========================================== + Coverage 40.94% 54.87% +13.93% =========================================== Files 99 96 -3 Lines 17462 17094 -368 =========================================== + Hits 7149 9380 +2231 + Misses 10313 7714 -2599 ``` | [Flag](https://app.codecov.io/gh/ClementTsang/bottom/pull/1474/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Clement+Tsang) | Coverage Δ | | |---|---|---| | [macos-12](https://app.codecov.io/gh/ClementTsang/bottom/pull/1474/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Clement+Tsang) | `36.36% <ø> (+0.04%)` | :arrow_up: | | [ubuntu-latest](https://app.codecov.io/gh/ClementTsang/bottom/pull/1474/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Clement+Tsang) | `56.37% <ø> (+13.47%)` | :arrow_up: | | [windows-2019](https://app.codecov.io/gh/ClementTsang/bottom/pull/1474/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Clement+Tsang) | `?` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Clement+Tsang#carryforward-flags-in-the-pull-request-comment) to find out more.

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[ClementTsang]

Oops, didn't realize I actually still use some of that code as backup process extraction - gonna close.