pager: advertise the config option in the default hgrc Same as for 'ui.color', this is a critical part of the UI and we want user to find this config knob easily.

pager: document the 'pager' config section There as a 'hg help pager' section but the 'hg help config.pager' was missing.

pager: test the 'enable' config option While poking at this option I realised it was not tested.

config: drop pager from the recommended extension The extension is deprecated, we should having exposing it to users.