Add powershell script to check emulator startup

[ishchow]

Adds powershell script similar to sh script to check if emulator startup completed by pinging emulator cert url.

Here's example output when startup fails (or emulator isn't running):

PS [redacted]> .\Check-EmulatorStartup.ps1 -Timeout $(New-TimeSpan -Seconds 30)
Emulator not reachable within timeout 00:00:30! Last retrieved status code: .
At C:\Repos\Mwc\aspaas\Deployment\scripts\Onebox\Check-EmulatorStartup.ps1:38 char:1
+ throw "Emulator not reachable within timeout $Timeout! Last retrieved ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : OperationStopped: (Emulator not re... status code: .:String) [], RuntimeException
    + FullyQualifiedErrorId : Emulator not reachable within timeout 00:00:30! Last retrieved status code: .

Here's example output when startup succeeds:

PS [redacted]> .\Check-EmulatorStartup.ps1 -Timeout $(New-TimeSpan -Seconds 30)
Emulator startup completed

Tested it on a Windows Server 2022 machine using PowerShell 5.1. But not using anything platform specific in this script, so it should be able to run in PS 7+ so it should work on all platforms PS 7+ supports.