GTK4 preparations

[leolost2605]

Some updates for GTK4:

• Remove unused libedataserverui dependency (the GTK4 version isn't available yet but it isn't used anyway)
• add (widget) -> child = widget wherever possible
• update margins, expand and homogeneous
• replace ButtonBoxes
• replace grid with box
• fix property bindings in ImapLoginPage
• use response.connect instead of run for dialogs
• Replace HAS_EDS_3_40 with version requirement because we currently have 3.44. That can be changed back though if necessary