Add support for login link (#4752)

* Add support for login link

https://mobile.element.io/element?account_provider=example.org&login_hint=mxid:@alice:example.org

* Update screenshots

* Reduce code duplication

* Add test on OnBoardingPresenter

* Fix tool

* Ignore login parameter if user is not allowed to connect to the provided server.

* Improve tests.

* Cleanup

* Revert change on Project.xml.

* Add documentation

* Improve LoginHelper

* Rename LoginFlow to LoginMode

Move LoginFlow to package io.element.android.features.login.impl.login
Rename some implementation of LoginMode
Rename LoginFlowView to LoginModeView

* Change launchMode of MainActivity from `singleTop` to `singleTask`

Using launchMode singleTask to avoid multiple instances of the Activity when the app is already open. This is important for incoming share and for opening the application from a mobile.element.io link.

Closes #4074

---------

Co-authored-by: ElementBot <android@element.io>

tests/uitests/src/test/snapshots/images/features.login.impl.screens.onboarding_OnBoardingView_Day_5_en.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:e93b2b62089570439aa10baf41d0ded8cdac23ba234a5bb32ba118f41e1f7385
+size 313315

tests/uitests/src/test/snapshots/images/features.login.impl.screens.onboarding_OnBoardingView_Night_5_en.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:aa123acbffde2545f7f76ce58ede9d1fb80668d2d8576bf5f920a49f91c1e474
+size 394540