Kernel Feature Freeze milestone in Impish Indri

[Setn Forshee]

In the past we've only had one real milestone for the kernel on the
release schedule, Kernel Freeze, which has served as a catch-all
milestone for kernel changes. This happens very late in the release
cycle for any substantial changes. However, the Feature Freeze milestone
is too early to freeze kernel features as we often do not have our final
upstream kernel release by then.

To remedy this situation we have added a new Kernel Feature Freeze
milestone to the Impish Indri release schedule [1]. This is the deadline
for all kernel feature work. The freeze is a few days before the Beta
Freeze to ensure we have a feature-complete kernel in the beta. Please
ensure that any feature work for the kernel has been submitted to the
kernel team mailing list before the freeze date.

Thanks,
Seth

[1] https://discourse.ubuntu.com/t/impish-indri-release-schedule/18540