Improve maintainability of dotnet tests

[laingsimon]

Some test fixtures are very long, due to complex setup; review if these can be simplified to reduce difficulties in maintaining the codebase.

• Introduce helpers/builders?
• Split up test fixtures into sub-fixtures

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Fixtures with 500+ lines:

File	Lines
UpdateScoresCommandTests.cs	681
DivisionDataDtoFactoryTests.cs	664
SeasonTemplateServiceTests.cs	642
DivisionServiceTests.cs	637
GameAdapterTests.cs	636
RequestedDivisionOnlyReportTests.cs	633
FinalsNightReportTests.cs	624
AddOrUpdateTeamCommandTests.cs	623
GameServiceTests.cs	610
DivisionFixtureAdapterTests.cs	559
DivisionDataGameVisitorTests.cs	557
DivisionFixtureDateAdapterTests.cs	542
DataServiceTests.cs	541
TemplateToHealthCheckAdapterTests.cs	509
WatchableDataDtoAdapterTests.cs	508
UserServiceTests.cs	508
FixtureDateAssignmentStrategyTests.cs	502

[laingsimon]

 get-childitem -recurse | where-object { $_.Name.EndsWith(".cs") -and $_.FullName.Contains("Tests") } | select-object @{ label='name'; expression={$_.name} }, @{ label='lines'; expression={(Get-Content $_.FullName | Measure-Object -Line).Lines} } | where-object { $_.lines -gt 500 } | sort-object -descending -property 'lines' | select-object { "| $($_.name) | $($_.lines) |" }