Rename legacy charts to something else

[snguyen64]

The current name of our "legacy" helm charts for retina is misleading as these charts are actively in use and not outdated.
"Legacy" creates confusion implying that it's obsolete, but that's not the case, we just have two different dataplanes which is supported.
I suggest changing the name to something like "basic" or any alternative.

[ritwikranjan]

As "basic" is already a used terminology in retina space. I was thinking we should go with a different one. I have "classic" in my mind. Let me know if there is any other suggestion!

[timraymond]

"Classic" still sounds deprecated in my mind. What about "Standard" instead as an alternative to "Basic"? That makes me think they're still "actively in use and not outdated" as @snguyen64 intends.