[Feature] Private README.md for organization

[changchaishi]

Implemented #29503

Changes:

1. Since individual users and organizations use the same .profile repository name for README.md, adding the private one, I rename the contexts with Public and Private inside them.
2. I wanted to load the private profile the same as GitHub, which uses the view_as query parameter. Still, the existing query scheme is quite limited due to the integration with the search form and the repository paginator, so my workaround is to forcefully bring augmented query strings of member/public to the tmpl file.
3. The drop-down is adopted from the search box's sort by component, we need to discuss the stylings.

Things lack and need further guidance:

1. At the create repository page, the ideal user experience is when the repo name is entered .profile the make repository private checkbox should be disabled and stay unchecked, whereas .profile-private, the checkbox should be disabled and force checked.
2. Follow 1., Tool tips should be added.
3. The translation and CSS for the current drop box and view as public/member feature.

Screenshots
Demo:

Need help:

[wxiaoguang]

It seems not easy as it looks.

The "view as" not only affects the "profile REAMDE", but also affects the repositories listed and other permission-related contents.