maintainer:release-notes: List other commits at the end

[damienmckenna]

The current maintainer:release-notes outputs commits based upon available d.o issues. However, commits which do not have corresponding d.o issues are ignored.

Proposal

Output commits which do not have corresponding d.o issues at the end of the current output with a heading of "Other commits".

[mglaman]

Flagging as a bug since it looses changes