Target dates for zfs-2.4.0

[tonyhutter]

There's been some interest in our schedule for zfs-2.4.0. Here's roughly what we were thinking:

• Mid August 2025: Create zfs-2.4.0-release branch and zfs-2.4.0-rc1 tag
• Aug-Oct 2025: Put out multiple release candidate (rc) tags for users to test.
• Nov 3 2025: Target date for zfs-2.4.0.

These dates are flexible. We're more concerned with having a solid, stable, release than hitting a self-imposed deadline.

[tonyhutter]

Edit: Changed release date from Nov 1st -> Nov 3rd so we can release on a Monday.