stand: mfc notes

MFCing stand is getting complicated. This file contains notes about
merging from 14, in summary:
o UFS changes have already been merged.
o The ZFS changes, on the whole, cannot be merged because OpenZFS

versions are different.

o MIPS is still present in 13, so commits to tear down mips

support.

o Some of the 14 GELI changes depend on crypto changes not yet merged.
o One change bumped the version to 14.x, and that shouldn't be merged.

The hashes listed should not be merged, unless something changes.

This is a direct commit to stable/13.