v6.0.0-alpha.17 release of PowerShellCore

Here are the major changes:

- Update PSRP client libraries for Linux and Mac.
  - We now support customer configurations for Office 365 interaction, as well as NTLM authentication for WSMan-based remoting from Linux (more information [here](https://github.com/PowerShell/psl-omi-provider/releases/tag/v1.0.0.18)). (#3271)
- We now support remote step-in debugging for `Invoke-Command -ComputerName`. (#3015)
- Use prettier formatter with `ConvertTo-Json` output. (#2787) (Thanks to @kittholland!)
- Port `*-CmsMessage` and `Get-PfxCertificate` cmdlets to Powershell Core. (#3224)
- `powershell -version` now returns version information for PowerShell Core. (#3115)
- Add the `-TimeOut` parameter to `Test-Connection`. (#2492)
- Add `ShouldProcess` support to `New-FileCatalog` and `Test-FileCatalog` (fixes `-WhatIf` and `-Confirm`). (#3074) (Thanks to @iSazonov!)
- Fix `Test-ModuleManifest` to normalize paths correctly before validating.
  - This fixes some problems when using `Publish-Module` on non-Windows platforms. (#3097)
- Remove the `AliasProperty Count` defined for `System.Array`.
  - This removes the extraneous `Count` property on some `ConvertFrom-Json` output. (#3231) (Thanks to @PetSerAl!)
- Port `Import-PowerShellDatafile` from PowerShell script to C#. (#2750) (Thanks to @powercode!)
- Add `-CustomMethod` paramter to web cmdlets to allow for non-standard method verbs. (#3142) (Thanks to @Lee303!)
- Fix web cmdlets to include the HTTP response in the exception when the response status code is not success. (#3201)
- Expose a process' parent process by adding the `CodeProperty Parent` to `System.Diagnostics.Process`. (#2850) (Thanks to @powercode!)
- Fix crash when converting a recursive array to a bool. (#3208) (Thanks to @PetSerAl!)
- Fix casting single element array to a generic collection. (#3170)
- Allow profile directory creation failures for Service Account scenarios. (#3244)
- Allow Windows' reserved device names (e.g. CON, PRN, AUX, etc.) to be used on non-Windows platforms. (#3252)
- Remove duplicate type definitions when reusing an `InitialSessionState` object to create another Runspace. (#3141)
- Fix `PSModuleInfo.CaptureLocals` to not do `ValidateAttribute` check when capturing existing variables from the caller's scope. (#3149)
- Fix a race bug in WSMan command plugin instance close operation. (#3203)
- Fix a problem where newly mounted volumes aren't available to modules that have already been loaded. (#3034)
- Remove year from PowerShell copyright banner at startup. (#3204) (Thanks to @kwiknick!)
- Fixed spelling for the property name `BiosSerialNumber` for `Get-ComputerInfo`. (#3167) (Thanks to @iSazonov!)
