[meta] Implement conditional logging and on-screen rendering in RulesDebugLoggingChannel

As outlined in the parent issue, we need a D8 replacement for the D7 RulesLog class, which was a transient singleton object used to collect (in memory) Rules debug messages so they could be optionally rendered as a debug log on the screen and optionally forwarded to the core dblog, controlled by Rules system variables, for storage in the database.

Steps that need to be taken:

1. Overhaul the Rules debug settings. #3102614: Change Rules configuration settings Assigned to: tr
2. Create a logger (not logger channel) analogous to DbLog which will be used to store Rules debug logs in a data structure. This will be the replacement for the D7 RulesLog class. #3103439: Create RulesDebugLog logger to hold temporary debug logs Assigned to: tr
3. Update RulesDebugLoggerChannel logger channel created by #3101194: Rename logger.channel.rules to logger.channel.rules_debug to use the new logger described above and to preprocess the variables supplied via log() so as to compute everything that needs to be stored for use in the on-screen log. #3103555: Update RulesDebugLoggerChannel Assigned to: tr
4. Implement code to retrieve logs and build render array from logs. Port all theming code - theme functions, JavaScript and CSS that was used in D7 to render and provide style and actions to the on-screen debug log. Conditionally display debug logs on screen (if settings permit) and (if settings permit) forward them to the system dblog. #3104109: Implement rendering of debug logs to screen and database Assigned to: tr