Since commit 01c96e78df ("Update DirectoryInfo handling for maildir"),
flags are checked for every message of a folder when entering it.
Iterating over all messages of a folder takes a long time for large
collections of emails.
Only count the number of messages and state that the directory info
counts are not accurate. Defer the parsing of message flags in
a goroutine to have a more responsive UI.
Fixes: https://todo.sr.ht/~rjarry/aerc/16
Suggested-by: Koni Marti <koni.marti@gmail.com>
Signed-off-by: Robin Jarry <robin@jarry.cc>
622802d3a5