Add default value for input boxes in tournament editor screens

[CloneWith]

Goal

In the current version of osu!lazer tournament client, there are small restore buttons that restore the current value of input boxes to their default. But most of them just revert to an empty string, which isn't so friendly in cases where we accidentally modified one and cannot easily undo this change unless restarting the client.

For this we can read values from the model, setting them default values on component loading. Then we can still access the initial value even after we save changes, as long as we haven't close the tournament client.