Display metrics overlay in the TV demo and add a dedicated setting

[MGaetan89]

Pull request

Description

This PR adds a new playback setting to enable or disable the metrics overlay. It also displays the metrics overlay based on that setting. I didn't add the text color and size settings, as we did on the mobile demo, but used the yellow text color and medium text size instead.

Changes made

• Add a playback setting in pillarbox-demo-tv to enable/disable the metrics overlay.
• Display the metrics overlay if the corresponding setting is enabled.
• Move MetricsOverlay to pillarbox-demo-shared.
• Add a shadow on the text of the MetricsOverlay to improve readability.
• Change the metrics overlay text size to 12sp, 14sp, 16sp to match Material's body small, body medium, and body large text sizes respectively. Let me know if you prefer to keep the original values.

Screenshots

Description	Screenshot
Metrics overlay setting disabled
Metrics overlay setting enabled
Metrics overlay displayed with controls visible
Metrics overlay displayed with controls hidden

Checklist

• Your branch has been rebased onto the main branch.
• APIs have been properly documented (if relevant).
• The documentation has been updated (if relevant).
• New unit tests have been written (if relevant).
• The demo has been updated (if relevant).
• All pull request status checks pass.

[github-actions]

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