Clean up TitleWindowManager.cs (#36327)

Clean up TitleWindowManager.cs (#36327)

* Clean up TitleWindowManager.cs

- I did not like how `OnHostnameChange()` always needed a string even though that string would always just be the hostname, so now it's just part of its function
- The extra function made to just trigger `OnHostnameChange()` are removed. It just runs the right function off the bat.
- Checking for `ClientRunLevel.InGame` for setting the title without the hostname, which means the previous joined server won't appear for a split second before being corrected by the new cvars being set. Or if the server prefers no host name in the titlebar by the time we connect.

* review

* Sus