Backports for GHC 9.0

Backports:

• !3640 (closed)
• !3848 (closed)
• !3730 (merged)
• !3831 (closed)
• !3859 (closed)
• !3808 (closed)
• !3822 (closed)
• !3624 (closed)
• !3800 (closed)
• !3798 (closed)
• !3797 (closed)
• !3801 (closed)
• !3775 (closed)
• !3763 (closed)
• !3727 (closed)
• !3497 (closed)
• !3761 (closed)
• !3751 (closed)
• !3736 (closed)
• !3756 (closed)
• !3755 (closed)
• !3754 (closed)
• !3746 (closed)
• !3720 (closed)
• !3745 (closed)
• !3708 (closed)
• !3616 (closed)
• !3615 (closed)
• !1675 (closed)

And a few minor documentation fixes