react-tabs: Added content and icon styles to subtle appearance

[GeoffCoxMSFT]

Current Behavior

Subtle tab content and icon not set.
This was due to moving styles into transparent that previously were on base.

New Behavior

Subtle tab content and icon styles applied per figma

Related Issue(s)

Related to #22336

[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 b8606f9:

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

[fabricteam]

📊 Bundle size report

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-components react-components: Accordion, Button, FluentProvider, Image, Menu, Popover	176.089 kB 49.113 kB
react-components react-components: FluentProvider & webLightTheme	32.601 kB 10.668 kB

_{🤖 This report was generated against 69bcdf2f52fe6a8bf7d5f7ca71be74d753202356}

[fabricteam]

Perf Analysis (@fluentui/react-components)

No significant results to display.

All results

Scenario	Render type	Master Ticks	PR Ticks	Iterations	Status
Avatar	mount	1043	1033	5000
Button	mount	623	620	5000
FluentProvider	mount	2070	2060	5000
FluentProviderWithTheme	mount	299	299	10
FluentProviderWithTheme	virtual-rerender	255	255	10
FluentProviderWithTheme	virtual-rerender-with-unmount	339	358	10
MakeStyles	mount	1796	1772	50000

[size-auditor]

Asset size changes

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

Baseline commit: 69bcdf2f52fe6a8bf7d5f7ca71be74d753202356 (build)