fix(Dropdown): Move scrollbar so it's reachable

[Hirse]

When using the Dropdown with multiple selection, it expands to at most three lines of selected items. When selecting even more items, a scrollbar appears.

Currently, the scrollbar shows up underneath the toggle indicator, making it inaccessible by mouse click.

This PR moves the scrollbar into the Dropdown content, to the left of the toggle indicator.

[DustyTheBot]

	Warnings
⚠️	There are no updates provided to CHANGELOG. Ensure there are no publicly visible changes introduced by this PR.

Perf comparison

Status	Scenario	Fluent TPI	Fabric TPI	Ratio	Iterations	Ticks
🔧	Avatar.Fluent	0.55	0.38	1.45:1	2000	1093
🔧	Button.Fluent	1.22	0.17	7.18:1	1000	1219
🔧	Checkbox.Fluent	1.34	0.28	4.79:1	1000	1338
🔧	Dialog.Fluent	0.32	0.16	2:1	5000	1621
🔧	Dropdown.Fluent	3.22	0.34	9.47:1	1000	3219
🔧	Icon.Fluent	0.24	0.03	8:1	5000	1193
🔧	Image.Fluent	0.09	0.07	1.29:1	5000	466
🔧	Slider.Fluent	1.83	0.28	6.54:1	1000	1828
🦄	Text.Fluent	0.05	0.15	0.33:1	5000	251
🦄	Tooltip.Fluent	0.33	17.31	0.02:1	5000	1652

🔧 Needs work     🎯 On target     🦄 Amazing

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