This will now readily happen when executed (not committed) success implicit keep
is replaced by a failure implicit keep.

mailbox_get_last_error() should be used only for client-visible errors.
The internal errors should be used for logging.

This was broken by recent adjustments to changes in Dovecot lib-storage API.

This allows side-effects to open a different mailbox than what is allocated
initially in act_store_start().

lib-sieve: store action: Allow side-effects to change the mailbox identifier used in action logging.

Use mailbox_get_last_error() shorthand rather than
mail_storage_get_last_error().

This way, the mailbox does not need to be opened until result execution.

The action name can be determined from the sieve_action_name field that existed
before.

Before it always used the name of the action definition, which is confusing e.g.
for the keep and fileinto actions, which both map to the same "store" action
definition.

Before, the virtual mailbox name was not sanitized, which caused control
characters to be displayed in log messages. Also, the mailbox name would be
mentioned twice in the log message, once santized and once unsanitized.

Now using struct smtp_address rather than sieve_address.
In some cases, struct message_address may prove to be more suitable, but this is the best fit for now.
Adjusted to the renamed fields in struct mail_deliver_context.

lib-sieve: store action: Avoid NULL pointer dereference during rollback when transaction context is somehow unassigned.

This change matches the other transaction stages.
This will not currently happen though.
Reported by Coverity.

lib-sieve: store action: Made static analyzer happier about tr_context argument for sieve_act_store_add_flags().

Added an assert ensuring it is not NULL.