fix(Dropdown): correctly generate loading and no results items

[silviuaavram]

Pull request checklist

• Addresses an existing issue: Fixes Dropdown: loading case has <li> contained by another <li> #12316
• Include a change request file using $ yarn change

Description of changes

Create the DropdownItem for loading / noResultsMessage the same way as it's created for normal items: with a shorthand that has children.

Focus areas to test

(optional)

Microsoft Reviewers: Open in CodeFlow

[msft-github-bot]

Perf Analysis

Scenario	Master Ticks	PR Ticks	Status
button	64	66	Possible regression

All results

Scenario	Master Ticks	PR Ticks	Status
BaseButton	761	731
BaseButton (experiments)	867	849
DefaultButton	1001	975
DefaultButton (experiments)	1742	1736
DetailsRow	3117	3175
DetailsRow (fast icons)	3155	3163
DetailsRow without styles	2952	2937
DocumentCardTitle with truncation	1598	1566
MenuButton	1305	1315
MenuButton (experiments)	3281	3288
PrimaryButton	1093	1121
PrimaryButton (experiments)	1828	1852
SplitButton	2768	2835
SplitButton (experiments)	6618	6563
Stack	425	430
Stack with Intrinsic children	998	1039
Stack with Text children	3741	3729
Text	339	341
Toggle	803	792
Toggle (experiments)	2107	2098
button	64	66	Possible regression

Perf Analysis (Fluent)

Perf comparison

Status	Scenario	Fluent TPI	Fabric TPI	Ratio	Iterations	Ticks
🔧	Avatar.Fluent	0.53	0.47	1.13:1	2000	1062
🦄	Button.Fluent	0.09	0.17	0.53:1	5000	448
🔧	Checkbox.Fluent	0.71	0.38	1.87:1	1000	711
🔧	Dialog.Fluent	0.39	0.19	2.05:1	5000	1931
🔧	Dropdown.Fluent	3.57	0.45	7.93:1	1000	3568
🔧	Icon.Fluent	0.16	0.05	3.2:1	5000	793
🦄	Image.Fluent	0.06	0.1	0.6:1	5000	318
🔧	Slider.Fluent	1.57	0.39	4.03:1	1000	1570
🔧	Text.Fluent	0.08	0.02	4:1	5000	378
🦄	Tooltip.Fluent	0.12	15.61	0.01:1	5000	609

🔧 Needs work     🎯 On target     🦄 Amazing

Perf tests with no regressions

Scenario	Current PR Ticks	Baseline Ticks	Ratio
FlexMinimalPerf.default	276	239	1.15:1
ButtonMinimalPerf.default	150	134	1.12:1
DropdownManyItemsPerf.default	1552	1452	1.07:1
DividerMinimalPerf.default	1002	951	1.05:1
BoxMinimalPerf.default	348	334	1.04:1
ButtonSlotsPerf.default	642	618	1.04:1
ChatDuplicateMessagesPerf.default	422	405	1.04:1
ChatMinimalPerf.default	578	558	1.04:1
ChatWithPopoverPerf.default	642	619	1.04:1
LayoutMinimalPerf.default	658	632	1.04:1
ListNestedPerf.default	954	920	1.04:1
ListWith60ListItems.default	1236	1183	1.04:1
DialogMinimalPerf.default	1944	1890	1.03:1
IconMinimalPerf.default	409	399	1.03:1
ListCommonPerf.default	1029	998	1.03:1
MenuMinimalPerf.default	2086	2027	1.03:1
PortalMinimalPerf.default	283	275	1.03:1
VideoMinimalPerf.default	879	852	1.03:1
AttachmentSlotsPerf.default	3742	3663	1.02:1
ToolbarMinimalPerf.default	1094	1071	1.02:1
Checkbox.Fluent	711	695	1.02:1
Icon.Fluent	793	778	1.02:1
Slider.Fluent	1570	1544	1.02:1
LabelMinimalPerf.default	350	347	1.01:1
RadioGroupMinimalPerf.default	536	533	1.01:1
RefMinimalPerf.default	194	193	1.01:1
SegmentMinimalPerf.default	1077	1065	1.01:1
TextAreaMinimalPerf.default	3158	3142	1.01:1
TooltipMinimalPerf.default	852	843	1.01:1
Avatar.Fluent	1062	1047	1.01:1
Dialog.Fluent	1931	1912	1.01:1
Tooltip.Fluent	609	600	1.01:1
AccordionMinimalPerf.default	228	229	1:1
AlertMinimalPerf.default	586	585	1:1
CarouselMinimalPerf.default	2127	2137	1:1
HierarchicalTreeMinimalPerf.default	990	989	1:1
ItemLayoutMinimalPerf.default	2059	2055	1:1
ListMinimalPerf.default	426	428	1:1
ProviderMergeThemesPerf.default	1374	1368	1:1
ProviderMinimalPerf.default	633	632	1:1
ReactionMinimalPerf.default	2504	2500	1:1
SliderMinimalPerf.default	1587	1591	1:1
StatusMinimalPerf.default	587	589	1:1
TreeMinimalPerf.default	1203	1202	1:1
Button.Fluent	448	448	1:1
AttachmentMinimalPerf.default	923	935	0.99:1
DropdownMinimalPerf.default	3615	3658	0.99:1
EmbedMinimalPerf.default	5583	5636	0.99:1
FormMinimalPerf.default	916	924	0.99:1
HeaderMinimalPerf.default	534	542	0.99:1
LoaderMinimalPerf.default	1076	1090	0.99:1
MenuButtonMinimalPerf.default	1523	1532	0.99:1
SplitButtonMinimalPerf.default	12502	12578	0.99:1
TextMinimalPerf.default	362	367	0.99:1
Dropdown.Fluent	3568	3603	0.99:1
CheckboxMinimalPerf.default	3282	3350	0.98:1
ImageMinimalPerf.default	319	324	0.98:1
PopupMinimalPerf.default	250	256	0.98:1
TableMinimalPerf.default	649	659	0.98:1
Image.Fluent	318	323	0.98:1
Text.Fluent	378	387	0.98:1
AnimationMinimalPerf.default	617	634	0.97:1
AvatarMinimalPerf.default	545	563	0.97:1
InputMinimalPerf.default	1050	1078	0.97:1
CustomToolbarPrototype.default	3670	3782	0.97:1
GridMinimalPerf.default	833	864	0.96:1
TreeWith60ListItems.default	220	229	0.96:1
HeaderSlotsPerf.default	1608	1706	0.94:1

[size-auditor]

Asset size changes

Size Auditor did not detect a change in bundle size for any component!

Baseline commit: da9745ae0b95cbc2c94b3400d96d8f3259841ca3 (build)