[keycloak-dev] Remove kcinit and text-based authentication flows

[Stian Thorgersen]

kcinit and it's associated text-based authentication flows adds quite a bit
of complexity. It was never fully completed and we don't have capacity to
complete it.

Text-based authentication flows are also not really all that useful. There
are other better approaches to authenticate devices without a web browser,
and when there is a web browser that should be used rather than cli.

I propose we remove both kcinit as well as the text-based authentication
flows. We also need to revert KeycloakInstalled to how it was prior to this
was added as it is currently fairly broken.