Fix handling of windows/buffers for non-nil completion-auto-select (bug#55712)

Fix handling of windows/buffers for non-nil completion-auto-select (bug#55712)

* lisp/minibuffer.el (completion--in-region-1): When completion-auto-select
is `second-tab', call switch-to-completions outside of `with-current-buffer'.
For the case of completion-auto-select customized to t,
move switch-to-completions from completion-setup-function
where it was called inside of with-current-buffer-window.

* lisp/simple.el (completion-setup-function): Move switch-to-completions
for completion-auto-select=t to completion--in-region-1 where it's
handled together with the case of `second-tab'.
(next-completion): Add check for the minibuffer to support in-buffer
inline completions.