[Feat]: make it more obvious when i am looking at smoothed data based on tiering

[andrewm4894]

Problem

in the UI there are no hints or signals that i am looking at smoothed data based on my tiering settings

in both images below the legend does not tell me i am not comparing like with like

Description

there should be something in the legend tooltip or somewhere that lets me easily understand when a charts data is smoothed based on tiered data.

Importance

must have

Value proposition

1. if we don't do this clearly we get dangerously close to "showing wrong data" imo which is a major no no.

Proposed implementation

add info to the legend tooltip in some way

[andrewm4894]

https://netdata-cloud.slack.com/archives/CS3PB0VJ7/p1695051153680129?thread_ts=1695051009.910179&cid=CS3PB0VJ7