proposed schedule for 8.1 release

[Peter Maydell]

Hi; I figured we could put some dates into the proposed 8.1
schedule. Here's a starter:

2023-07-11 Soft feature freeze
2023-07-18 Hard feature freeze. Tag rc0
2023-07-25 Tag rc1
2023-08-01 Tag rc2
2023-08-08 Tag rc3
2023-08-15 Release; or tag rc4 if needed
2023-08-22 Release if we needed an rc4

(dates picked largely to ensure that we don't slip into
September)

Richard, you're doing merges, so the most important
question is whether this works for you :-)

thanks
-- PMM