Do not show violin plots with a sample size less than 5

[creilly8]

Description

Closes issue #2618. Will show the item as uncomputable in the legend instead.

Test with this violin example. Should see four values as uncomputable because of sample size.

Checklist

Check each task that has been performed or verified to be not applicable.

• Tests: added and/or passed unit and integration tests, or N/A
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• Notable Changes: updated release.txt, prefixed a commit message with "fix:" or "feat:", added to an internal tracking document, or N/A

[creilly8]

@airenzp, quick question - Why is the legend set so uncomputable values only appear for the continuous term? In the example above the continuous term is term but all the plots are values of term2/overlayTerm. An uncomputable value would never show in this instance.

[xzhou82]

violin should work the same as boxplot.

in this example there are groups <=5 only showing dots but no boxplot; violin should do same to only show "bead plot" on client, and do not compute violin on server, and render violin on client