feat(xunit logging): TestOutputHelperWireMockLogger

[Stepami]

Description

Current implementation of the TestOutputHelperWireMockLogger obligates me to always have ready-to-use not null instance of ITestOutputHelper. It makes it quite uncomfortable to provide logging in cases when the WireMockServer is wrapped up in a xUnit fixture.

This PR extends applications of the TestOutputHelperWireMockLogger by allowing it to be constructed with Func<ITestOutputHelper>

Use Case

public class WireMockFixture
{
    public WireMockFixture()
    {
        WireMockServer = WireMockServer.Start(
            new WireMockServerSettings
            {
                Logger = new TestOutputHelperWireMockLogger(() => TestOutputHelper)
            });
    }

    public WireMockServer WireMockServer { get; }

    public void Dispose()
    {
        WireMockServer.Dispose();
        TestOutputHelper = null;
    }

    public ITestOutputHelper? TestOutputHelper { get; set; }
}

[CollectionDefinition(nameof(WireMockCollection))]
public class WireMockCollection : ICollectionFixture<WireMockFixture>;

[Collection(nameof(WireMockCollection))]
public class Tests
{
    public Tests(WireMockFixture fixture, ITestOutputHelper testOutputHelper)
    {
        fixture.TestOutputHelper = testOutputHelper;
    }
}