feat(ngAria): add support for ignoring a specific element

[gkalpak]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Feature

What is the current behavior? (You can also link to an open issue here)
It is not possible to force ngAria to "ignore" a specific element, i.e. not add aria-* attributes, attach roles, bind keyboard events etc. The only work-around is to provide those attributes yourself (in which case ngAria won't overwrite them), but this is tedious and doesn't work for all usecases.

What is the new behavior (if this is a feature change)?
It is possible to force ngAria to "ignore" a specific element, by adding the ng-aria-disable attribute.

Does this PR introduce a breaking change?
No.

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#commit-message-format
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Other information:
Fixes #14602
Fixes #14672

[gkalpak]

/cc @marcysutton

Notes:

• The current implementation will only ignore the specific element, not the whole subtree. I thought about adding support for ignoring the whole subtree, but:
  1. The implementation would be more involved (e.g. we might need to traverse up the DOM looking for an attribute or we could have a directive and require its controller from all ngAria directives).
  2. Unless there is a strong (valid) usecase, we should not promote (or make it easy) to disable ngAria in large parts of the DOM.
• A possible future enhancement is to disable specific features. E.g. ng-aria-disable="ariaHidden, bindRoleForClick, tabindex".

[marcysutton]

I like this idea; it would also help to address the config being global in #11174.

It makes sense that disabling would only work for that specific node...crawling DOM subtrees would be too expensive. I like the future enhancement of disabling certain features, that was my one question after reviewing the PR.

[Narretz]

LGTM, but must be rebased (and possibly updated if something has been added to ngAria)

[gkalpak]

Rebased. (AFAICT, nothing has been added to ngAria that is not accounted for.)

[Splaktar]

Just in case anyone (like me) is looking for when this feature was released, it was first available in 1.7.1.