API: Allow prop=info intestactions to return reasons

API: Allow prop=info intestactions to return reasons

T194585 raises a use case for callers to be able to know why an action
is not allowed. We can make that possible easily enough. The default
remains to return only a boolean.

This also deprecates inprop=readable in favor of intestactions=read,
since they both just return `$title->userCan( 'read', $user )`.

(ApiQueryInfoTest added by David Barratt)

Bug: T194585
Change-Id: Ib880f0605880eac776d816ea04e0c7ab9cfbaab1
Co-Authored-By: David Barratt <dbarratt@wikimedia.org>