Two effects keyed on the account list reloaded every connected login each
time the list changed - and while a browser restores its logins it changes
once per connection, so the cost was 1 + 2 + … + N:
- useProMultiAccountMailboxes, which the Pro shell runs for its per-account
folder tree, reloaded every login's folders: 55 Mailbox/get with ten logins.
It now loads each login once per client, through the same cache as the
unified scope, and reloads all of them once on an account switch.
- useProMultiAccountIdentities reread every other login's identities: 45
Identity/get. Each mount now reads each account once; what is already
known shows at once, and a read that outlives the run that started it
still reaches the dropdown.
Both are keyed on the set of connected logins instead of `accounts`, which
also changes for display-name and login-time updates.
lucamzanon
612dcc81ee