Compiler test cleanup, part 3 (and the last one)

[psfinaki]

Part of the: #13654

Finalizes the efforts started here and here.

This merges:

• FSharp.Compiler.Service.Tests (nUnit)
• FSharp.Compiler.UnitTests (xUnit)
• tests/service (nUnit)

... to one suite (xUnit), thus removing cognitive load and bringing us closer to being full xUnit.

Also:

• unskips some tests which were skipped due to now-resolved issues
• turns on some warnings which were turned on due to now-resolved issues
• removes some random hacks from project files
• aligns module names
• removes some old dead tests which were not being compiled and not compiling (and not worth bringing back to life)

This doesn't affect the CI time significantly:

[psfinaki]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[psfinaki]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

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cc @dotnet/fsharp-team-msft

[vzarytovskii]

As a separate PR/issue, I think we also should fix reports, as now it just shows "NUnit_TestResults_***", like here https://dev.azure.com/dnceng-public/public/_build/results?buildId=688529&view=ms.vss-test-web.build-test-results-tab

We need to fix it with name of the "leg" test is running on.

[psfinaki]

As a separate PR/issue, I think we also should fix reports, as now it just shows "NUnit_TestResults_***", like here https://dev.azure.com/dnceng-public/public/_build/results?buildId=688529&view=ms.vss-test-web.build-test-results-tab

We need to fix it with name of the "leg" test is running on.

Yes, I also noticed that. Would prefer to do it separately, added to the related ticket.