Breaking change

It is no longer necessary to provide a list of entities to monitor for each template platform as automatic analysis can now find all entities that affect the state in the template ...

Proposed change

As a part of the "Month of WTH," the request for global variables came up. This PR (in draft while it is considered, modified, etc.) adds a variables integration....

Not the faux global variables implemented by various custom components but first-class citizens of Home Assistant.  We should be able to define a global string, integer, float, list, dict. Even just a string that holds more than a mere 255 characters would be appreciated. The state of global variables would be saved on shutdown and restored on startup.  That’s not asking for a lot considering what kind of global variables can be defined in another home automation system (that’s now 20 years old)...