Demote user log entries from "notice" to "info".

Problem/Motivation

Currently a number of user activities log messages at a "notice" level that are more correctly categorized as "info" messages, per RFC 5424, namely:

* User Registration notices
* User Login notices
* User Role additions / updates
* User Password Recovery Requests
* User using "one time" login link
* User sessions start / end
* User accounts blocked / deleted
* User Flood control notices

In all of the above instances, when these messages are logged the system is actually functioning as designed, and logging these events is truly "informational" in nature.

Proposed resolution

Let's lower the log message Severity level to one more appropriate, and log these as info events, not notices.

User interface changes

The user login and related messages are now styles as "info" messages rather than "notice" messages.

Before

After

Release notes snippet

Log level changes

Some routine user events which were previously logged as notices are now logged at the lower-severity "info" level. A change record lists which user events are now logged at the "info" level → .