feat(material-experimental/*): Add focus indicators to all MDC except mdc-chips.

[zelliott]

• Added focus indicators to all MDC components that have demo pages and need focus indicators (except chips).
• Implementation is essentially identical to that for Angular Material. Uses mat-mdc- prefixes (e.g .mat-mdc-focus-indicator, @include mat-mdc-strong-focus-indicators, etc...).
• Added unit tests that ensure the class is present.

[jelbourn]

LGTM, though I'd like to have @mmalerba, @crisbeto, and @devversion also take a look since they actually worked on this stuff

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[googlebot]

CLAs look good, thanks!

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[mmalerba]

LGTM

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