Remove View Cached Windows And Buffers

`View.tabpages` and `BUFNR_PER_TAB` are cached an not always correct. See #2624

Remove the caches and always determine the actual.

Ensure no O(n) calls to `View.`
```
get_bufnr
is_visible
get_winnr
open_in_win
abandon_current_window
abandon_all_windows
_prevent_buffer_override
```