Combobox: Set role='combobox' on input element

[bxiao]

Fixes #2753

According to the Aria 1.2 spec for combobox https://www.w3.org/TR/wai-aria-practices-1.2/examples/combobox/combobox-autocomplete-list.html, the role="combobox" attribute should be set on the inner input element, not the containing div.

Additional description

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[interactivellama]

@bxiao This is bigger than just moving the role attribute.

From an open work ticket: W-8074194
Currently, Salesforce uses the ARIA 1.1 markup for comboboxes. Screen readers announce the new markup better, so we should update to the 1.2 version. Need to move the following attributes to the text input:

role="combobox"
aria-expanded
aria-haspopup="listbox"

The div will just be a wrapper for styles now, it won't have any of the combobox attributes.

[interactivellama]

Also, as you mentioned on Slack. Please update all variants that have the div role=combobox attribute.

[interactivellama]

See comments