Improved testability of several host configurators

Recently, I wanted to test if my `HostConfigurator` set-up method would correctly set-up the host configurator to run as a local system account (by calling `RunAsLocalSystem` on it). I tried to write a unit test for this, but this failed due to not being able to access the actual account type passed to the `RunAsServiceAccountHostConfigurator` instance created when the `RunAsLocalSystem` extension method was called on my `HostConfigurator`. 

The solution was simple: replace the read-only private field `_accountType` with a read-only public property. This now allowed me to write the desired unit test:

    [Fact]
    public void RunAsLocalSystemAddsRunAsServiceAccountHostConfiguratorWithLocalSystemAsServiceAccount()
    {
        // Arrange
        var hostConfiguratorMock = new Mock<HostConfigurator>();
            
        // Act
        hostConfiguratorMock.Object.RunAsLocalSystem();

        // Assert
        hostConfiguratorMock.Verify(h => h.AddConfigurator(It.Is<RunAsServiceAccountHostConfigurator>(c => c.AccountType == ServiceAccount.LocalSystem)), Times.Once);
    }

I have also gone through the other configurator classes and done the same thing. This will also make them testable.