refactor(react-switch): add base state hooks for Switch component

[Copilot]

Introduces base state hooks for Switch following the pattern established in #35697 (Persona) and #35709 (MessageBar).

Changes

• Types: Added SwitchBaseProps and SwitchBaseState that exclude design prop (size)
• Hook: Added useSwitchBase_unstable containing core behavior (refs, slots, a11y, labelPosition)
• Exports: New types and hook exported at component/library level; commented in main index.ts for experimental branch

Usage

// Custom Switch variant without size prop
const state = useSwitchBase_unstable(baseProps, ref);

// Full hook composes base + size prop
const state = useSwitch_unstable(props, ref);
// Internally calls useSwitchBase_unstable

API Surface

Export	Type
useSwitchBase_unstable	Hook
SwitchBaseProps	Type
SwitchBaseState	Type

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[github-actions]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
react-components react-components: entire library	1.291 MB 322.866 kB	1.291 MB 322.908 kB	38 B 42 B
react-switch Switch	34.502 kB 10.827 kB	34.536 kB 10.832 kB	34 B 5 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-components react-components: Button, FluentProvider & webLightTheme	70.308 kB 19.905 kB
react-components react-components: Accordion, Button, FluentProvider, Image, Menu, Popover	237.217 kB 68.47 kB
react-components react-components: FluentProvider & webLightTheme	43.523 kB 13.978 kB
react-portal-compat PortalCompatProvider	8.386 kB 2.624 kB
react-timepicker-compat TimePicker	108.15 kB 35.693 kB

_{🤖 This report was generated against 8f7d1cc6974c5bbe6f2539ae8590ccd02cd00441}

[github-actions]

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