refactor(material-experimental/mdc-progress-bar): remove wrapper element for progress bar

[annieyw]

refactor progress bar to have same structure as progress spinner (without wrapper element)

related: #22429

[annieyw]

Seems like the issue with the tests is that the original progress bar has a wrapper div around the different bars but as discussed in #22429 progress bar and progress spinner should have the same a11y setup. Any ideas on which we should prioritize? (align with original progress bar or have mdc progress bar/spinner have same a11y)

[crisbeto]

The changes LGTM. I think that we should keep the DOM as close to MDC as possible and update the tests to expect more than one root node inside the progress bar. I don't think that screen readers care whether it's one root node with aria-hidden or multiple siblings with aria-hidden.

[annieyw]

Animations were still running with NoopAnimationsModule with the previous fix. Added some more specific selectors to disable animations (like in progress spinner)

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