Add a textfield autocomplete version of the "Project navigate" block

For #364383: Alter "Project navigation" block form to add a "View issues" button and #201435: Huge list of projects hard to use, consumes excessive d.o. bandwidth, can hang browser it'd be better to have a textfield autocomplete version of the "Project navigate" block. I've got a patch, that depends on #364395: project/autocomplete is broken.