Set Label on Bubble in Bubble Chart

Hi,

**Want to update Values(label) in bubble entries in bubble chart.**

Start by locating the bubble chart entry and its label/value handling in the Swift chart code. Determine how bubble labels are currently represented and what updating them should mean, then check existing bubble chart tests or examples if available. Done means bubble entries expose the requested label update behavior, with coverage or a reproducible example demonstrating it.

Written by the indexing model from the issue text.