Change Details

``` ui is one of the modules that poison other modules with boost/signals2 headers. This moves the include to the cpp file and uses a forward declaration in the header. ``` Backport of core PR13634.

``` ui is one of the modules that poison other modules with boost/signals2 headers. This moves the include to the cpp file and uses a forward declaration in the header. ``` Backport of core [[https://github.com/bitcoin/bitcoin/pull/13634/files | PR13634]].

``` ui is one of the modules that poison other modules with boost/signals2 headers. This moves the include to the cpp file and uses a forward declaration in the header. ``` Backport of core [[https://github.com/bitcoin/bitcoin/pull/13634/files | PR13634]].