fix: Pickers' live region announcement text is removed from the DOM

[smhigley]

Previous Behavior

We fire an invisible live region when selected tags are removed, but since we don't clear the text, it's discoverable with a screen reader's virtual cursor.

New Behavior

We can remove the live region text on a timeout so it will still fire the event and be read by screen readers, but the text will not remain in the DOM/accessibility tree in between the label and form field.

• Fixes 15715

[size-auditor]

Asset size changes

Project	Bundle	Baseline Size	New Size	Difference
office-ui-fabric-react	fluentui-react-Pickers	279.781 kB	279.858 kB	77 bytes

 Over Tolerance (1024 B)  Over Baseline  Below Baseline  New   Removed 1 kB = 1000 B

Baseline commit: cf10f5be18439d0c0c3f53baac7f996237569691 (build)

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 646a8f1:

Sandbox	Source
@fluentui/react 8 starter	Configuration
@fluentui/react-components 9 starter	Configuration

[fabricteam]

📊 Bundle size report

_{🤖 This report was generated against cf10f5be18439d0c0c3f53baac7f996237569691}

[fabricteam]

🕵 fluentuiv8 Open the Visual Regressions report to inspect the 4 screenshots

✅ There was 4 screenshots added, 0 screenshots removed, 1041 screenshots unchanged, 0 screenshots with different dimensions and 0 screenshots with visible difference.

unknown 4 screenshots

Image Name	Diff(in Pixels)	Image Type
Pivot - Overflow.Root.Narrow - Last tab selected.chromium.png	0	Added
Pivot - Overflow.Root.Narrow - Overflow menu.chromium.png	0	Added
Pivot - Overflow.Tabs - RTL.Narrow - Last tab selected.chromium.png	0	Added
Pivot - Overflow.Tabs - RTL.Narrow - Overflow menu.chromium.png	0	Added

[fabricteam]

Perf Analysis (@fluentui/react)

Scenario	Render type	Master Ticks	PR Ticks	Iterations	Status
GroupedList	mount	2327	2654	2	Possible regression

All results

Scenario	Render type	Master Ticks	PR Ticks	Iterations	Status
BaseButton	mount	1488	1493	5000
Breadcrumb	mount	3828	3628	1000
Checkbox	mount	3342	3311	5000
CheckboxBase	mount	3060	3015	5000
ChoiceGroup	mount	5595	5516	5000
ComboBox	mount	1615	1616	1000
CommandBar	mount	11945	12249	1000
ContextualMenu	mount	13784	13459	1000
DefaultButton	mount	1699	1713	5000
DetailsRow	mount	4429	4457	5000
DetailsRowFast	mount	4538	4441	5000
DetailsRowNoStyles	mount	4296	4277	5000
Dialog	mount	3781	3825	1000
DocumentCardTitle	mount	716	716	1000
Dropdown	mount	4015	3982	5000
FocusTrapZone	mount	2574	2524	5000
FocusZone	mount	2427	2499	5000
GroupedList	mount	2327	2654	2	Possible regression
GroupedList	virtual-rerender	1439	1416	2
GroupedList	virtual-rerender-with-unmount	2042	2073	2
GroupedListV2	mount	721	702	2
GroupedListV2	virtual-rerender	675	689	2
GroupedListV2	virtual-rerender-with-unmount	714	709	2
IconButton	mount	2400	2389	5000
Label	mount	899	905	5000
Layer	mount	5338	5438	5000
Link	mount	1062	1042	5000
MenuButton	mount	2103	2137	5000
MessageBar	mount	2940	2917	5000
Nav	mount	4044	4046	1000
OverflowSet	mount	1741	1728	5000
Panel	mount	3199	3200	1000
Persona	mount	1654	1600	1000
Pivot	mount	2015	2053	1000
PrimaryButton	mount	1911	1872	5000
Rating	mount	8648	8701	5000
SearchBox	mount	1920	1906	5000
Shimmer	mount	3569	3536	5000
Slider	mount	2611	2682	5000
SpinButton	mount	5768	5845	5000
Spinner	mount	1019	1014	5000
SplitButton	mount	3817	3877	5000
Stack	mount	1014	1031	5000
StackWithIntrinsicChildren	mount	2972	2913	5000
StackWithTextChildren	mount	5939	5925	5000
SwatchColorPicker	mount	12878	12967	5000
TagPicker	mount	3211	3264	5000
TeachingBubble	mount	105506	106261	5000
Text	mount	992	994	5000
TextField	mount	2062	2032	5000
ThemeProvider	mount	1898	1911	5000
ThemeProvider	virtual-rerender	1386	1369	5000
ThemeProvider	virtual-rerender-with-unmount	2699	2691	5000
Toggle	mount	1373	1391	5000
buttonNative	mount	668	708	5000