Integrate new XY Chart theme value labels styling

[dej611]

Since v.24.0.0 elastic-charts ships an improved value labels feature, currently merged in Lens with a theme customization.

As suggested by @markov00 this theme customization should be integrated into EUI.

[elizabetdev]

I'm also linking this issue elastic/elastic-charts#886 where we discussing the use of the value labels.

[github-actions]

👋 Hey there. This issue hasn't had any activity for 180 days. We'll automatically close it if that trend continues for another week. If you feel this issue is still valid and needs attention please let us know with a comment.

[github-actions]

❌ We're automatically closing this issue due to lack of activity. Please comment if you feel this was done in error.

[cchaos]

Ugh, this issue should have been skipped because it has an assignee.

[wylieconlon]

Following up on this since we just got a user asking about it. Seems like we've made a decision to reduce the default border, but it's not implemented yet?

[elizabetdev]

@wylieconlon I'll prioritize this issue.

The decision is to not use the border (or yes, to use it but very discrete). Borders should be used when we have multiple background colors. For instance, a label on top of a map. When we only have one background color we can improve the contrast of the label so the border is not necessary. It only creates more distractions.