fix(list): case where list items are read twice by screen readers

[Splaktar]

PR Checklist

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• The commit message follows our guidelines
• Tests for the changes have been added or this is not a bug fix / enhancement
• Docs have been added, updated, or were not required

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

When a clickable / linkable md-list-item is provided without an aria-label, the directive creates a button/link with an aria-label. Because this element and the original inner contents are siblings, asking a screen reader to read through the document results in both the created link and the content to be read, which is awkward for screen reader users.

Issue Number:
Fixes #11582

What is the new behavior?

• if we create an aria-label from the element's text content then mark the content as aria-hidden="true" so that screen readers don't announce/traverse the content twice
• improve Closure types

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information