Addresses some observed gaps in behaviors with connections. This is
unfortunately mainly a patch without fully understanding the deep issue
being avoided but it seems reasonable for the experimental branch.

…ode-hierarchy

Conflicts:
	core/block_svg.ts

It seems that the extra safety checks weren't actually needed.

More investigation and fixes are likely still needed.

Only one behavioral change was needed.

Fixes ARIA ownership for these connection types.

…ode-hierarchy

Conflicts:
	core/block_svg.ts

Addresses a review comment.