[Visualization Panels] Sharp Edges

[Erikg346]

Describe the feature:

Allow the ability to change the edges of Visualization panels in dashboards to sharp and square-like edges

Describe a specific use case for the feature:
I appreciate the update made to the dashboards panels #178139, I think it can be improved on my make panels more appealing by making them square.

Currently,

Proposed:

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)

[nreese]

@andreadelrio @teresaalvarezsoler thoughts on this request?

[andreadelrio]

This change would have to come from our design system so that Dashboards' styles match the rest of Kibana. I will bring this up with the team working on the new theme.