Make tree items more actionable and add AppAction for expanding the object tree (#5997)

* style: add `visibility` to tree expand triangles

- The purpose of this is so that Playwright can perform actionability checks on the tree items. This will make operations involving expanding tree items much easier to perform in e2e.

* feat(e2e): Add AppAction to expand the entire tree

* fix: wait for loading indicator

* test: add test for `expandEntireTree`

* test: update `expandEntireTree` and tree selectors

- Use dynamic aria-label for different tree implementations

- Get rid of CSS ids which are only for testing

- Update percy tree scope selector

* chore(lint): remove unused variable

* refactor(e2e): update tree locators

Co-authored-by: John Hill <john.c.hill@nasa.gov>

e2e/tests/visual/components/tree.visual.spec.js

@@ -57,7 +57,7 @@ test.describe('Visual - Tree Pane', () => {
             name: 'Z Clock'
         });
 
-        const treePane = "#tree-pane";
+        const treePane = "[role=tree][aria-label='Main Tree']";
 
         await percySnapshot(page, `Tree Pane w/ collapsed tree (theme: ${theme})`, {
             scope: treePane
@@ -94,7 +94,7 @@ test.describe('Visual - Tree Pane', () => {
  * @param {string} name
  */
 async function expandTreePaneItemByName(page, name) {
-    const treePane = page.locator('#tree-pane');
+    const treePane = page.getByTestId('tree-pane');
     const treeItem = treePane.locator(`role=treeitem[expanded=false][name=/${name}/]`);
     const expandTriangle = treeItem.locator('.c-disclosure-triangle');
     await expandTriangle.click();