fix(material/form-field): make notch sizing more reliable

[mmalerba]

Swap out the current logic for determining when to resize the outline gap, for logic based on ResizeObserver. The current logic tries to guess when the size may need to change based on observing the content, checking after fonts load, etc. But using ResizeObserver should catch more cases.

Also brings the gap calculation logic outside the NgZone to avoid running unnecessary change detections.

[github-actions[bot]]

Deployed dev-app to: https://ng-dev-previews-comp--pr-angular-components-26028-e02f-qfra092t.web.app

Note: As new commits are pushed to this pull request, this link is updated after the preview is rebuilt.

[mmalerba]

This is ready for another look

[mmalerba]

ready for review again

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