Remove the Settings Tray dependency on Toolbar

There is a bunch more delicate unpicking to be done here, there are multiple references to toolbar in settings_tray that need to be moved out.

Hm, settings_tray depends on contextual which in turn depends on toolbar.. seems we need to make both settings_tray and contextual also work with navigation before we can disentangle this from toolbar.

I've just tried out Settings Tray on an Umami install; it seems to do not really work at all while Navigation is installed, whether Toolbar is installed or not. I had to install Toolbar and uninstall Navigation before the "Quick edit" contextual links worked properly for me.

There doesn't seem to be an issue for this but some brief discussion in #3421969-81: [PLAN] New Navigation and Top Bar to replace Toolbar Roadmap: Path to Stable, Gabor then raised this over at #3484850-4: [meta] Tasks to deprecate Toolbar module but there has been no followup.

Assuming we do #3576315: [policy, no patch] Move Settings Tray to a contributed project first this will become a non-issue - contrib settings tray can depend on contrib toolbar.

Nothing came up in the 4 months inbetween and settings tray is on the verge of bring removed also, so moving to won't fix for good :)