[v6] Expose current container to BeforeContainer

[fflaten]

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• I have tested using the latest version of Pester. See Installation and update guide.

Summary of the feature request

To provide conditional setup for different containers like if ($current -like '*.Integration.Tests.ps1'), BeforeContainer scripts need a reference to the current container

How should it work?

Expose a variable with the current container name (fullpath on File, else <ScriptBlock>)