fix: set role application and fix block readouts

[maribethb]

The basics

• I validated my changes

The details

Resolves

Fixes #9666

Proposed Changes

• Sets role=application on the blockly subcontainer
• Sets block labels and other aria states on the focusable element of the block, not its svg root
• sets role=presentation on the block's svgRoot to exclude the extraneous elements from the accessibility tree. this matches what we've done in the screenreader experiment branch

Reason for Changes

block labels weren't being read correctly because the browser focuses the path object's svg path, not the block's svg root. now the methods call the block's getFocusableElement so that the roles are set on the focused element (even if in the future that element becomes e.g. the svg root rather than the path object)

Test Coverage

updated tests to assert on the correct focusable element as well

Documentation

Additional Information