Update outlined text field to handle leading and trailing icon

[lynnmercier]

Update outlined text field to handle leading and trailing icon. This is a CSS update. (I don't think there are any JS involved here....)

[kfranqueiro]

FYI there is some JS involved in emitting an event when the leading/trailing icon is interacted with. It is currently handled from a listener at the root of the component.

material-components-web/packages/mdc-textfield/foundation.js

Line 147 in b12c576

this.adapter_.notifyIconAction();