dcc: refactor slider #312

Job	Run time
Build Dash Package	3m 31s
Detect Relevant Path Changes	5s
Typing Tests	2m 46s
Run Background & Async Callback Tests (Python ${{ matrix.python-version }})	0s
Table Unit/Lint Tests (Python ${{ matrix.python-version }})	-1s
Table Server Tests (Group ${{ matrix.test-group }})	-1s
	6m 20s

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