Fix no session set when replaceMWLogin is true

The session is normally set by SpecialUserlogin, when this is replaced, there
will no session setup and the login/create account will normally fail. Check
in SpecialPage if the session is already setup or setup by yourself.

Bug: 69199
Change-Id: Ib80abbcce7747104a1fa51fee52abc5af52b5f4d
(cherry picked from commit a12ac08d9620df51c91d723180507574516596b1)
Fix WebInstaller-Break

Set wgAuth only, if GoogleLoginAuth exists and move this setup
into wgExtensionFunctions.
Fix type in Documentation of GoogleLoginAuth

Bug: 69564
Change-Id: I6e18e61cc721ca069e3cbbce9787d429344b7474
(cherry picked from commit f7bb3f99ee6e033a3db27c019d33c4fd873e34df)
Fix automatic set of wgAuth

Change-Id: I33b157e28d1ad928aa204fda3287bf10c0f95ceb
(cherry picked from commit e04f380dbabab0b6b2ff803399091d4505412235)