dcc redesign: refactor `Loading` component #447

Job	Run time
Build Dash Package	2m 55s
Detect Relevant Path Changes	7s
Typing Tests	2m 49s
Table Unit/Lint Tests (Python ${{ matrix.python-version }})	0s
Run Background & Async Callback Tests (Python ${{ matrix.python-version }})	0s
Table Server Tests (Group ${{ matrix.test-group }})	0s
	5m 51s

Provide feedback