feat(MatChipEditInput): Add aria-label attribute to MatChipEditInput directive

[clamli]

Feature Description

Add a general aria-label to MatChipEditInput like "editable chip", and consider removing the tabindex="-1" set by this directive.

Use Case

This will resolve the aria-input-field-name violation when the chip turns into editable mode.

[crisbeto]

Setting a lower priority on this, because users can project their own edit input on which they can set the label. Doing this on our end isn't as straightforward, because we don't have a good way of localizing the label.