[TreeView] disableSelection does not disable all selections

[tonyhallett]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

1. Only click is disabled
2. Single select tree item when not selected will have aria-selected=false

Expected Behavior 🤔

1. Expect all selection to be disabled.

2. If the tree does not support multiple selection, aria-selected is set to true for the selected node and it is not present on any other node in the tree.

Steps to Reproduce 🕹

https://codesandbox.io/s/silly-knuth-yidwl

Steps:

1. Focus Apples
2. Press space - Apples is selected

2. Click the button

Context 🔦

Trying to disable selection.
Expecting aria authoring practices

[eps1lon]

"incorrect aria-selected for single select" was fixed in #20102

[eps1lon]

Closed in #20146. GitHub decided to ignore this.