fetch-configlet.ps1: fix for newer PowerShell versions

[ErikSchierboom]

• scripts(ps1): fix command chaining
• scripts(ps1): move to where it is needed
• scripts(ps1): use name field to exactly match filename
• scripts(ps1): test if script is run from repo root
• scripts(ps1): add message for downloading
• scripts(ps1): replace broken expand-archive with ZipFile
• scripts(ps1): use explicit output filename
• scripts(ps1): output download info

Closes #839

[ee7]

Thanks - merging! I'm not a PowerShell user, but this seems sane. I guess it broke due to a PowerShell version update. I haven't seen a failure in the fetch-configlet CI job - but maybe the PowerShell version there is still good, or it hasn't been run recently enough.

I'll try to add PSScriptAnalyzer to the configlet CI, especially since we already have shellcheck for other scripts.