This introduces ember-a11y-testing to acceptance tests via a helper
wrapper that allows us to globally ignore rules that we can address
separately. It also adds fixes for the aXe rules that were failing.
This is mostly a direct application of the ember-angle-brackets-codemod.
I manually restored newlines in multi-line component invocations, usually
preserving file line length except for now-non-positional link-to @route.
I needed to rename task to taskState in some cases to avoid Ember
Concurrency naming conflicts.
