It's been sometime since we introduced this new safety enhancing feature
bit. At this point, we're now moving to require it as it makes our SCB
recovery system more robust, and it's also an implicit feature bit for
for anchor commitments as they're defined now.
This commit introduces a feature.Manager, which derives feature vectors
for various contexts within the daemon. The sets can be described via a
staticly compiled format, which makes any runtime adjustments to the
feature sets when the manager is initialized.
