Calcite-components: Tree: active indicators

[bstifle]

1. Remove ability to use the active/hover indicator bar PLUS the •. Would be better to have only 1 of those at a time.

2. add the ability to have checkmarks in place of the • if using multi select.

[cosbyr]

@macandcheese I second this one. The tree is looking a little cluttered now in our app.

[macandcheese]

Suggestion: when lines enabled, keep JUST the bar. When lines is disabled, keep JUST the dot cc @capeoples

[macandcheese]

Multi select should also use "check" vs. single dot indicator with no lines.