Startup perf test

perftest.ps1

$num = 50
$ps = @("powershell.exe", "C:\Program Files\PowerShell\6\pwsh.exe", "C:\Program Files\PowerShell\7-preview\pwsh.exe")
$ps | ForEach-Object {
    $thisps = $_
    $psv = & $thisps -nop -c '$psv = $psversiontable.gitcommitid; if ($psv -eq $null) { $psv = $psversiontable.psversion.tostring() }; $psv'
    [int]$i = 0
    1..$num | ForEach-Object {
        $i += (Measure-Command {
            & $thisps -nop -c exit
        }).TotalMilliseconds
    }
    [PSCustomObject]@{
        PSVersion = $psv
        "Time (ms)" = $i / $num
    }
}