bring the server-selection option back for advanced user

### Your use case

#### What would you like to do?
user could choose default or self-hosted server at first
#### Why would you like to do it?
matrix.org blocked in China,so chinese users do nothing but waiting a long time even doubt element been blocked like youtube,etc
#### How would you like to achieve it?

### Have you considered any alternatives?

1.remove "register" or "already have.."
2.initial screen could be server-select ,user could choose
- simple-one （default matrix.org）
- advanced

3.the input box of name & pass with "sign-up" & "sign-in" buttons

that's so easy..

### Additional context

_No response_

### Are you willing to provide a PR?

No