fix(react-drawer): apply position: absolute when mountNode is passed

[marcosmoura]

Previous Behavior

Drawer would always render using position: fixed, to be displayed as a root element.

New Behavior

In case mountNode is passed, Drawer will now render as position: absolute to be contained in the target element.

Related Issue(s)

• Fixes [Bug]: Drawer overlays entire screen instead of area it's placed in #29132

[fabricteam]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
react-components react-components: entire library	1.1 MB 271.811 kB	1.1 MB 271.862 kB	142 B 51 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-components react-components: Button, FluentProvider & webLightTheme	69.14 kB 20.137 kB
react-components react-components: Accordion, Button, FluentProvider, Image, Menu, Popover	218.197 kB 63.203 kB
react-components react-components: FluentProvider & webLightTheme	44.447 kB 14.59 kB
react-portal-compat PortalCompatProvider	8.39 kB 2.64 kB
react-timepicker-compat TimePicker	107.387 kB 35.758 kB

_{🤖 This report was generated against 6cae9b1a85188bf343d73c1b52c18138042fc714}

[fabricteam]

Perf Analysis (@fluentui/react-components)

No significant results to display.

All results

Scenario	Render type	Master Ticks	PR Ticks	Iterations	Status
Avatar	mount	609	619	5000
Button	mount	301	312	5000
Field	mount	1148	1152	5000
FluentProvider	mount	717	730	5000
FluentProviderWithTheme	mount	88	90	10
FluentProviderWithTheme	virtual-rerender	38	34	10
FluentProviderWithTheme	virtual-rerender-with-unmount	80	81	10
MakeStyles	mount	871	866	50000
Persona	mount	1756	1748	5000
SpinButton	mount	1401	1361	5000
SwatchPicker	mount	1629	1701	5000

[mainframev]

LGTM, few small suggestions