Fix '-PipelineVariable' to set variable in the right scope

[daxian-dbw]

PR Summary

Fix #16155

Fix '-PipelineVariable' to set variable in the right scope and to not remove the pipeline variable at the end of pipeline when it's actually using an already existing variable.

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[iSazonov]

Have we the same issue for other variables like OutVariable?

[daxian-dbw]

No, only pipeline variable is special.

[ghost]

🎉v7.3.0-preview.1 has been released which incorporates this pull request.:tada:

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