Setup tests on additional platforms that .NET Standard supports

[clambertus]

We have recently setup an Azure DevOps YAML build configuration, which makes adding testing environments easier to our CI process. Adding tests to ensure support on macOS and Linux has been completed already, and (fortunately) the number of bugs that were found was fairly minimal (most of them were addressed in beta00006). However, there are other platforms .NET Standard supports that are commonly in use by Lucene.NET users which we should also setup our tests to run on.

Looking through the JIRA and GitHub issues, 4 platforms that have been mentioned are:

• Mono
• UWP - UWP is now deprecated
• Xamarin iOS
• [ ] .NET MAUI
• [x] .NET Framework x86
• [x] .NET 6

We should do a survey to find out what other platforms may be commonly in use and make the determination how important it is to test on them, and of course take into consideration whether the tests require a special setup that Azure Pipelines doesn't provide on any of the Microsoft-hosted agents.

JIRA link - [LUCENENET-633] created by nightowl888

[NightOwl888]

MAUI will be a release candidate in April, 2022.

There are a set of xUnit tests noted here: https://github.com/dotnet/maui/issues/2112#issuecomment-1073307339. Looks like no specialized runner is required like was the case on Xamarin, so NUnit should work (in theory).