Get rid of ambiguous OutputType::NONE value
Based on suggestion by Pieter Wuille <firstname.lastname@example.org> at
After #12119, the NONE output type was overloaded to refer to either an output
type that couldn't be parsed, or to an automatic change output mode. This
change drops the NONE enum and uses a simple bool indicate parse failure, and a
new CHANGE_AUTO enum to refer the change output type.
This change is almost a pure refactoring except it makes RPCs reject empty
string ("") address types instead of treating them like they were unset. This
simplifies the parsing code a little bit and could prevent RPC usage mistakes.
It's noted in the release notes.
This is a backprt of Core PR12729
Reviewers: #bitcoin_abc, jasonbcox
Reviewed By: #bitcoin_abc, jasonbcox
Differential Revision: https://reviews.bitcoinabc.org/D4423