PS: Add ZipSlip query

[MathiasVP]

This PR adds another classic query: finding zip slip vulnerabilities.

The query works in the sense that it does find what its supposed to find. i.e., it detects:

$zip = [System.IO.Compression.ZipFile]::OpenRead("MyPath\to\archive.zip")
foreach ($entry in $zip.Entries) {
    $targetPath = Join-Path $extractPath $entry.FullName
    [System.IO.Compression.ZipFileExtensions]::ExtractToFile($entry, $targetPath) # BAD
}

However, because we haven't added support for proper barriers guards to PowerShell we currently also flags this false positive:

foreach ($entry in $zip.Entries) {
    $targetPath = Join-Path $extractPath $entry.FullName
    $fullTargetPath = [System.IO.Path]::GetFullPath($targetPath)

    $extractRoot = [System.IO.Path]::GetFullPath($extractPath)
    if ($fullTargetPath.StartsWith($extractRoot)) {
        [System.IO.Compression.ZipFileExtensions]::ExtractToFile($entry, $fullTargetPath) # GOOD [FALSE POSITIVE]
    }
}

I'll use this motivation to start working on proper barrier guard support for PowerShell soon. That should be relatively easy now that GitHub has added a shared guards library.

Commit-by-commit review recommended. It took quite a lot of small improvement in various internal libraries to get this working. In particular:

• 1f775b9 adds another user-facing API to API graphs so that we can mark zip.Entities as a flow source.
• 9916bbb adds the actual query.
• 8d3f6b8 adds query tests. At this point they all fail, but we'll fix that in the subsequence commits.
• ca2cf5e adds some much-needed flow summaries needed to get the tests working. 869c613 also adds separate tests for these summaries.

I then discovered a bug in the control-flow class for foreach: the predicate for getting the "iterable" part of a foreach (i.e, xs in foreach(x in xs) { ... }) didn't work because it has some special handling in the control-flow graph. So 831f25d adds a test for this and 2ec78ed fixes this.

I then discovered another bug around foreach loops: we didn't have a read step from xs to x in:

foreach(x in xs) {
 ...
}

So 4276405 adds a test for this and 5692eb0 fixes this.

And finally the query now detects the required cases as demonstrated by 93a3833 🎉

Along the way I also did a drive-by improvement to DataFlow::ObjectCreationNode in ca20eb5. This was needed for an earlier version of the query, but ended up not being necessary in the end. It is still a valuable change, though.