fix: STORE for iCloud and other strict IMAP servers

[ralflang]

This is Anna's PR #30 but against FRAMEWORK_6_0

Apple's iCloud IMAP server (and possibly others, although I haven't tested it) want brackets around any FLAG command params as shown in the examples of RFC3501 If the brackets aren't added, the command fails with BAD Parse Error To fix this, wrap the params of a STORE command in a Horde_Imap_Client_Data_Format_List Otherwise, the \Delete FLAG, \Seen FLAG and possibly all other PERMFLAGs aren't added, even if the STORE command doesn't return a BAD response.

[what-the-diff]

PR Summary

• Improved code usage in Socket.php
  The respective changes in this file aim to enhance how the FLAGS value is set in the $cmds array. We switched from a direct use of replace and add/remove values to a more efficient usage of Horde_Imap_Client_Data_Format_List class. This adjustment correlates with better consistency in data format management and can potentially lead to fewer bugs in the future.