[Feature Request] Add PowerShell Core Support

[pauby]

Just a recommendation, currently run script.ps1 will encounter:

Exception setting "SecurityProtocol": "The requested security protocol is not supported."
At C:\Program Files\PowerShell\Modules\au\2018.5.18\Public\Update-Package.ps1:384 char:5
+     [System.Net.ServicePointManager]::SecurityProtocol = 'Ssl3,Tls,Tl ...
+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : NotSpecified: (:) [], SetValueInvocationException
+ FullyQualifiedErrorId : ExceptionWhenSetting

and

Get-WebFile : Exception calling "IsBypassed" with "1" argument(s): "Operation is not supported on this platform."
At C:\Users\Ruiyang\AppData\Local\Temp\chocolatey\au\chocolatey\helpers\functions\Get-ChocolateyWebFile.ps1:345 char:7
+       Get-WebFile -Url $url -FileName $fileFullPath -Options $options
+       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : NotSpecified: (:) [Get-WebFile], MethodInvocationException
+ FullyQualifiedErrorId : PlatformNotSupportedException,Get-WebFile

Issue migrated from majkinetor/au#158

[Tucug]

Until now, PowerShell-core worked for us.
We observed that the last versions of PowerShell-core introduce an incompatibility with Au update scripts:

Running update_all with PowerShell-core 7.2.6 is successful.
Running update_all with PowerShell-core 7.3.2 results in the following error

VERBOSE: Failed mypackage
   [1/1] myPackage ERROR:
     Chocolatey v1.2.1 File specified is either not found or not a .nupkg file. 'myPackage.myVersion.nupkg ' (7.81s)

The regression is probably introduced for all versions of PowerShell-core 7.3
Please note the additional space in the nupkg string which might point to the issue.

Issue observed with chocolatey versions 1.1, 1.2, and 1.3 (no matter the choco version). Observed with PowerShell-core 7.3.2 and 7.3.3
Issue not observed with chocolatey version 1.1 + PowerShell 7.2.6
Issue not observed with chocolatey version 1.3 + PowerShell 7.2.6

I let the maintainer @pauby decide if it should be a separate bug issue or if here is fine.

[pauby]

@totofelder Can you raise a separate issue for this?

Issue not observed with chocolatey versions 1.1 and 1.3 with PowerShell 7.2.6

Could you clarify the issue wasn't observed with 1.2 because you didn't test it, or because it didn't happen?

[flcdrg]

Created separate issue for PS regression - #24