Move reroute settings to reroute settings page or show a summary

Problem/Motivation

Currently, the reroute settings (email address) have to be entered in the mailer policy, which needs more clicks and isn't that simple to find, while the module provides an option to enable or disable at /admin/config/system/mailer/reroute

Typically, when you enable the setting you wish to see where the email goes, so it would be great for UX, if the recipient address could be shown on the enable / disable page or be set there.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes