(Angular/CDK) Expose more methods from interactivity-checker

I want to use some methods like isNativeFormElement, isHiddenInput, isInputElement and isAnchorElement from interactivity-checker, but I find they are not accessible from InteractivityChecker service. eg: isNativeFormElement https://github.com/angular/material2/blob/master/src/cdk/a11y/interactivity-checker.ts#L155

Can we move those functions into the InteractivityChecker service so that we can access them?

[changLiuUNSW]

We mainly use them for accessibility purpose. For example:

1. Find find first native form element and trigger focus. (isNativeFormElement)
2. Find element with tabIdex=-1 and trigger focus. (getTabIndexValue)
3. Find first focusable elements and trigger focus. (isPotentiallyFocusable)

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