Tabs - change border bottom API

[wise-king-sullyman]

Is this a new component or an extension of an existing one?
Refactoring of an existing component's API and change of default behavior.

Describe the feature
Currently primary tabs have a full width bottom border by default (and consumers can opt out of that behavior by setting the hasBorderBottom prop to false), but secondary tabs have to opt into that behavior using the hasSecondaryBorderBottom prop.

This API could be made more intuitive by both primary and secondary tabs having the same default behavior. This would allow the hasSecondaryBorderBottom to be removed and hasBorderBottom to control the bottom border behavior regardless of whether the tabs are primary or secondary.

Comment where this breaking change was suggested: #7311 (comment)

dependent on core issue #5128