Use colorScheme for chat variables

[Hirse]

Cleans up all Chat-related styles by

• Moving from siteVars.colors to siteVars.colorScheme
  • Except for hasMentionColor as that has some special handling (see fix(Chat Message): update at mention colors fluent-ui-react#1232)
    @codepretty Do you remember what the reason is to have different colors for at-mention bar and nubbin?
• Remove not needed theme overrides
• Sort variables alphabetically

There are no changes to any styling results.

[DustyTheBot]

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

Generated by 🚫 dangerJS against 3cae6ea

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Latest deployment of this branch, based on commit 3cae6ea:

Sandbox	Source
Fluent UI React Starter	Configuration

[size-auditor]

Asset size changes

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

Baseline commit: 874be4906a0177df3316e2a15a88dc699836bca9 (build)

[fabricteam]

📊 Bundle size report

_{🤖 This report was generated against 874be4906a0177df3316e2a15a88dc699836bca9}

[fabricteam]

Perf Analysis (@fluentui/react)

Scenario	Render type	Master Ticks	PR Ticks	Iterations	Status
DocumentCardTitle	mount	144	138	1000	Possible regression

All results

Scenario	Render type	Master Ticks	PR Ticks	Iterations	Status
Avatar	mount	778	817	5000
BaseButton	mount	860	873	5000
Breadcrumb	mount	2582	2588	1000
ButtonNext	mount	530	533	5000
Checkbox	mount	1492	1474	5000
CheckboxBase	mount	1275	1289	5000
ChoiceGroup	mount	4690	4668	5000
ComboBox	mount	984	971	1000
CommandBar	mount	10030	10026	1000
ContextualMenu	mount	6266	6202	1000
DefaultButton	mount	1124	1100	5000
DetailsRow	mount	3694	3709	5000
DetailsRowFast	mount	3692	3687	5000
DetailsRowNoStyles	mount	3468	3468	5000
Dialog	mount	2203	2095	1000
DocumentCardTitle	mount	144	138	1000	Possible regression
Dropdown	mount	3177	3195	5000
FluentProviderNext	mount	7224	7260	5000
FocusTrapZone	mount	1757	1770	5000
FocusZone	mount	1799	1769	5000
IconButton	mount	1701	1707	5000
Label	mount	334	330	5000
Layer	mount	1734	1767	5000
Link	mount	467	457	5000
MakeStyles	mount	1797	1776	50000
MenuButton	mount	1448	1447	5000
MessageBar	mount	1996	2012	5000
Nav	mount	3233	3172	1000
OverflowSet	mount	1028	1037	5000
Panel	mount	2080	2038	1000
Persona	mount	814	814	1000
Pivot	mount	1370	1394	1000
PrimaryButton	mount	1260	1235	5000
Rating	mount	7526	7532	5000
SearchBox	mount	1323	1319	5000
Shimmer	mount	2512	2474	5000
Slider	mount	1944	1938	5000
SpinButton	mount	4888	4939	5000
Spinner	mount	395	408	5000
SplitButton	mount	3154	3108	5000
Stack	mount	490	494	5000
StackWithIntrinsicChildren	mount	1477	1478	5000
StackWithTextChildren	mount	4410	4408	5000
SwatchColorPicker	mount	9977	9955	5000
Tabs	mount	1507	1390	1000
TagPicker	mount	2380	2352	5000
TeachingBubble	mount	11846	11801	5000
Text	mount	400	401	5000
TextField	mount	1338	1313	5000
ThemeProvider	mount	1133	1159	5000
ThemeProvider	virtual-rerender	583	606	5000
Toggle	mount	779	788	5000
buttonNative	mount	115	104	5000

Perf Analysis (@fluentui/react-northstar)

⚠️ 2 potential perf regressions detected

Potential regressions comparing to master

Scenario	Current PR Ticks	Baseline Ticks	Ratio	Regression Analysis
AttachmentMinimalPerf.default	148	140	1.06:1	analysis
AccordionMinimalPerf.default	145	138	1.05:1	analysis

Perf tests with no regressions

Scenario	Current PR Ticks	Baseline Ticks	Ratio
AvatarMinimalPerf.default	192	178	1.08:1
AnimationMinimalPerf.default	421	392	1.07:1
IconMinimalPerf.default	623	583	1.07:1
RadioGroupMinimalPerf.default	449	423	1.06:1
TreeWith60ListItems.default	170	162	1.05:1
AlertMinimalPerf.default	264	254	1.04:1
AttachmentSlotsPerf.default	1064	1027	1.04:1
RefMinimalPerf.default	241	231	1.04:1
TableMinimalPerf.default	400	383	1.04:1
ButtonMinimalPerf.default	162	158	1.03:1
CardMinimalPerf.default	534	519	1.03:1
ChatMinimalPerf.default	639	622	1.03:1
ChatWithPopoverPerf.default	359	347	1.03:1
ItemLayoutMinimalPerf.default	1219	1178	1.03:1
ListCommonPerf.default	632	613	1.03:1
ListMinimalPerf.default	510	495	1.03:1
ListNestedPerf.default	551	535	1.03:1
ReactionMinimalPerf.default	373	361	1.03:1
StatusMinimalPerf.default	670	650	1.03:1
TooltipMinimalPerf.default	1002	975	1.03:1
GridMinimalPerf.default	330	323	1.02:1
LayoutMinimalPerf.default	363	355	1.02:1
MenuMinimalPerf.default	828	815	1.02:1
SkeletonMinimalPerf.default	348	340	1.02:1
TreeMinimalPerf.default	777	763	1.02:1
BoxMinimalPerf.default	338	334	1.01:1
ButtonOverridesMissPerf.default	1653	1632	1.01:1
DatepickerMinimalPerf.default	5318	5277	1.01:1
DropdownMinimalPerf.default	3074	3040	1.01:1
FlexMinimalPerf.default	275	272	1.01:1
HeaderMinimalPerf.default	354	349	1.01:1
HeaderSlotsPerf.default	749	741	1.01:1
PortalMinimalPerf.default	172	171	1.01:1
ProviderMinimalPerf.default	953	946	1.01:1
TextMinimalPerf.default	340	336	1.01:1
CustomToolbarPrototype.default	3764	3737	1.01:1
ToolbarMinimalPerf.default	915	904	1.01:1
CarouselMinimalPerf.default	440	438	1:1
CheckboxMinimalPerf.default	2701	2694	1:1
DialogMinimalPerf.default	733	736	1:1
DropdownManyItemsPerf.default	667	665	1:1
EmbedMinimalPerf.default	4026	4035	1:1
FormMinimalPerf.default	393	393	1:1
InputMinimalPerf.default	1227	1222	1:1
LabelMinimalPerf.default	373	373	1:1
LoaderMinimalPerf.default	686	685	1:1
PopupMinimalPerf.default	581	583	1:1
SplitButtonMinimalPerf.default	3667	3675	1:1
ChatDuplicateMessagesPerf.default	286	288	0.99:1
ImageMinimalPerf.default	358	360	0.99:1
MenuButtonMinimalPerf.default	1583	1596	0.99:1
SliderMinimalPerf.default	1505	1520	0.99:1
TableManyItemsPerf.default	1842	1860	0.99:1
TextAreaMinimalPerf.default	486	492	0.99:1
VideoMinimalPerf.default	596	605	0.99:1
ListWith60ListItems.default	630	646	0.98:1
ProviderMergeThemesPerf.default	1658	1690	0.98:1
ButtonSlotsPerf.default	506	519	0.97:1
SegmentMinimalPerf.default	331	340	0.97:1
RosterPerf.default	1111	1163	0.96:1
DividerMinimalPerf.default	338	358	0.94:1

[ling1726]

Remove not needed theme overrides

Does that mean these overrides were never used ?

[Hirse]

Does that mean these overrides were never used?

No, I meant an example like this:
Default theme sets chat-background to siteVars.colors.grey[100], which gets set to siteVars.colors.grey[800] by dark theme, though both are actually siteVars.colorScheme.default.background2.
By setting default theme to the color-scheme value, the override in dark theme (and v2 themes in this case) are no longer necessary.