Fix T6646, Show signature status in ribbon for filesystem Emails
* src/oomhelp.h: define constant for PR_INTERNET_MESSAGE_ID_W_DASL
* src/oomhelp.cpp: In get_unique_id if GPGOL_UID_DASL is not found and
should not be created try to use
PR_INTERNET_MESSAGE_ID_W_DASL as ID
* src/ribbon-callbacks.cpp: Search via searchMailsByUUID and use first
mail found instead of getMailByUUID.Mails from filesystem don't have a GPGOL_UID property alos EntryID is
not set so we fallvak and use the Message-ID to find the email to
update the ribbon status icons.