Add CommandLine property to Process

[iSazonov]

PR Summary

Fix #3322 on Windows and Linux. For MacOs we will open new tracking issue to implement later.

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[adityapatwardhan]

@iSazonov can you give a before and after for a perf comparison? Call Get-CimInstance or Get-Content for every System.Diagnostics.Process object sounds expensive.

The test can be as simple as:

Measure-command { 1..100 | % { get-process } }

[iSazonov]

@adityapatwardhan It is "on demand" property - you evaluate it only if you explicitly call the property. But if you call you get a slowdown. It is not in default output so users don't see slowdown in common scenarios.
Notice, I found WMI is very fast on latest Windows versions (Windows 10 and Windows Server 2019). If someone provides feedback that it's still slow we could consider a P/Invoke.
On Linux /proc works fast.
For MacOs I do not know API. I am going to open new tracking issue for this after the PR will be merged.

[SteveL-MSFT]

For both Linux and macOS, I wonder if it would be ok to run ps to cache the command lines and map it to the object?

[iSazonov]

Using /proc is simple and reliable on Linux so no need to create a workaround.
I haven't Mac and can not create even a workaround. Nonetheless I hope there is a good API for that.

[adityapatwardhan]

@TravisEz13 @JamesWTruher Do you know of a macOS workaround for this?

[adityapatwardhan]

@iSazonov I am not sure if we should take this PR without having a solution for all platforms. This introduces gotchas and makes cross platform scripting difficult.

@iSazonov @SteveL-MSFT - thoughts?

[iSazonov]

My plan is to open a tracking issue for MacOs. We have a lot of time before release and can investigate how enhance the feature on MacOs.

[powercode]

The APIs will probably require some native coding on the mac.

We can probably use the same apis as top.

https://opensource.apple.com/source/top/top-111.20.1/libtop.c.auto.html

[ghost]

This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Mainainer, Please provide feedback and/or mark it as Waiting on Author

[adityapatwardhan]

@iSazonov Please open a tracking bug for macOS and also open a issue for documentation as per the PR template.

[iSazonov]

@adityapatwardhan Tracking issue #12832

As for doc issue - do we really need to document this? It seems we haven't docs for extended properties at all.
/cc @sdwheeler

[sdwheeler]

@iSazonov No, we don't document the extended properties. But this is worth adding to the release notes.

[adityapatwardhan]

@iSazonov Thank you for your contribution!

[ghost]

🎉v7.1.0-preview.4 has been released which incorporates this pull request.:tada:

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