fix(analytics-chart): arrange legend items in grid when horiz [MA-2011]

[filipgutica]

Summary

• When legend display is horizontal, arrange items in a grid
• Also truncate long labels and provide a tooltip on hover when legend display is horizontal

https://konghq.atlassian.net/jira/software/c/projects/MA/issues/MA-2011

PR Checklist

• Naming & Structure: the files and package structure use the conventions outlined in the Creating a Package docs.
• Tests pass: check the output of all package unit and/or component tests.
  • If this PR is the result of a bug, test coverage was added accordingly.
• Functional: all changes do not break existing APIs, but if so, a BREAKING CHANGE commit is in place to bump the major version.
• Conventional Commits all commits follow the conventional commit standards outlined in the main README.
• Docs: includes a technically accurate README, and the docs have been updated accordingly based on the changes in this PR.

[mihai-peteu]

I would go aggressively small here, 4px for both column-gap and row-gap, which equates to$kui-space-20.

And on L187 , for .legend-container li, the margin all around could be as small as 8px ($kui-space-40)