Add checks that ProcessName is not null or empty.

* Disambiguate icon for daily builds on Windows.
Some code had to be borrowed from build.psm1 because this script has to be self contained in case it gets executed by only downloading this file via the published download link https://twitter.com/Steve_MSFT/status/930585082451992576

…Shell#5537)

* updated install link and instructions for R-Pi
* remove libicu57 as it's not needed

* XML documentation fix for CompletionResult: 1 typo, make text start with upper case and add periods at the end.
This typo showed up on the official docs site: https://docs.microsoft.com/en-us/dotnet/api/system.management.automation.completionresult.-ctor?view=powershellsdk-1.1.0#System_Management_Automation_CompletionResult__ctor_System_String_

* Add periods to private members as well as suggested in PR.

…Shell#5498)

This resolves issue PowerShell#5391, which is tagged with 6.0.0-GA, therefore this should help with getting pwsh out of the door in January.

It removes PerformWSManPluginReportCompletion as stated in the issue and its associated class member g_pPluginContext, which is now unused as well.

The best reviewer is probably @mirichmo , who raised the initial issue with very helpful descriptions or @dantraMSFT who is currently assigned to the issue.

reducing the base image size should make the build a little faster
Also, remove the duplicate upload of a file