fix(panel): allow transform to be animated on an offset panel

[Splaktar]

Previously, if a panel had a position with an offset (e.g. $mdPanel.newPanelPosition().center()), the positioning would break any transform animations on the panel. This was due to the fact that mdPanel uses inline transform styles to do the offsetting. These changes introduce a wrapper around the panel (.md-panel-inner-wrapper), which will handle all of the positioning, allowing for any animations to be applied to the .md-panel itself.

Relates to #9641.
Fixes #9905.

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What kind of change does this PR introduce?

[ ] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
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[ ] CI related changes
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What is the current behavior?

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Does this PR introduce a breaking change?

[ ] Yes
[ ] No

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