fix(material-experimental/chips): high contrast mode fixes (#16811)
fix(material-experimental/chips): high contrast mode fixes (#16811)

Fixes the following issues with the MDC-based chips in high contrast mode:
* Chips blending in with the background because they don't have an outline or a border.
* No focus indication being visible.
* Chips being hidden completely on hover because we were using an RGBA overlay.
angular/components,crisbeto/material2,angular/components,Jefiozie/material2,mmalerba/material2,DevVersion/material2,DevVersion/material2,Jefiozie/material2,jelbourn/material2,Jefiozie/material2,jelbourn/material2,angular/components,andrewseguin/material2,andrewseguin/material2,josephperrott/material2,andrewseguin/material2,crisbeto/material2,crisbeto/material2,josephperrott/material2,jelbourn/material2,mmalerba/material2,josephperrott/material2,angular/components,DevVersion/material2,DevVersion/material2,andrewseguin/material2,josephperrott/material2,Jefiozie/material2,Jefiozie/material2,mmalerba/material2,jelbourn/material2,josephperrott/material2,mmalerba/material2,crisbeto/material2,andrewseguin/material2,DevVersion/material2,mmalerba/material2,jelbourn/material2