patch 9.1.1084: Unable to persistently ignore events in a window and its buffers

patch 9.1.1084: Unable to persistently ignore events in a window and its buffers

Problem:  Unable to persistently ignore events in a window and its buffers.
Solution: Add 'eventignorewin' option to ignore events in a window and buffer
          (Luuk van Baal)

Add the window-local 'eventignorewin' option that is analogous to
'eventignore', but applies to a certain window and its buffers. Identify
events that should be allowed in 'eventignorewin', adapt "auto_event"
and "event_tab" to encode this information. Window context is not passed
onto apply_autocmds_group(), and when to ignore an event is a bit
ambiguous when "buf" is not "curbuf", rather than a large refactor, only
ignore an event when all windows into "buf" are ignoring the event.

closes: #16530

Signed-off-by: Luuk van Baal <luukvbaal@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>