Move entity "Last updated" to the attributes section?

[deviantintegral]

Following up from home-assistant/home-assistant.io#23900

As a user who doesn't have knowledge of the internals of Home Assistant, I think the most common interpretation would be:

1. Last changed: The state value last changed at that time.
2. Last updated: The sensor last reported an unchanged state value.

In practice, "Last updated" represents a timestamp when the state value didn't change, but entity attributes did (it's also updated when the value changes). However, many entities don't define any attributes but still show the last updated timestamp in the UI.

Even if they do define attributes, the information hierarchy seems off. If the last updated timestamp is related to attributes, it should be shown inside the attribute section. This is especially confusing for sensors showing history graphs with the extra height between the date and the attributes section:

Could we move the last updated date into the attributes section? Then it's hidden if an entity has no attributes, and it's clear what drives it updating.

This was originally added to the tooltip in #6926

[frenck]

These are not attributes. But properties of the state object.

They are documented and the last update is shown on the state.