An earlier version of #16546 used both --with-boost-process and --enable-external-signer, which was simplified to only use the latter. However I forgot to update CI, so the external signer tests were not run.
This reverts the changes made in merge commit
1b307613604883daea4913a65da30ae073c9dc4d:
This reverts commit b919efadff.
This reverts commit d54f64c6c7.
This reverts commit 787f40668d.
This reverts commit d630646662.
This reverts commit e6e44eedd5.