imap: extend detection patterns - v7

[mmaatuq]

Ticket: #2886

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Link to redmine ticket:2886

Describe changes:

• extend detection patterns for imap protocol as per rfc9051
• compared to this previous PR: rebase to latest master.
• this is not comprehensive and might create more false positives, but i think this tradeoff is acceptable, and we can overcome these limitations when we add a complete parser.

SV_BRANCH=https://github.com/OISF/suricata-verify/pull/1915