The decorator form can now be used with bound methods after a fix
for the related bug was merged. Mention this in docs and release
notes, so that people are aware of it.
A new test is added to make sure this also works with class methods
(as well as to check that the proposed decorator applying order
is actually correct).
Related-Bug: #1520195
Change-Id: Ifea08114d6d89de9d67fcae397eb94c0afc4d339
8a5fbb723f