Add ToolUtilities to define tool icon as a React element (backport #1150)

[mergify]

Changes

Add ToolUtilities.defineIcon helper that defines an icon as a React element for a given ToolType.

For additional information and usage notes see NextVersion.md

Testing

Added additional unit tests and tested via test-app.

---

This is an automatic backport of pull request #1150 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 87ca8e3 has failed:

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Changes to be committed:
	modified:   apps/test-app/src/frontend/appui/frontstages/MainFrontstage.tsx
	modified:   common/api/appui-react.api.md
	modified:   common/api/imodel-components-react.api.md
	modified:   common/api/summary/appui-react.exports.csv
	modified:   common/api/summary/imodel-components-react.exports.csv
	new file:   common/changes/@itwin/appui-react/tool-icons_2024-12-11-13-21.json
	new file:   common/changes/@itwin/imodel-components-react/tool-icons_2024-12-11-13-21.json
	modified:   e2e-tests/tests/toolbar/toolbar-composer.test.ts-snapshots/toolbar-composer-test-1-chromium-linux.png
	new file:   ui/appui-react/src/appui-react/icons/SvgViewLayouts.tsx
	renamed:    ui/appui-react/src/appui-react/tools/KeyinPaletteTools.ts -> ui/appui-react/src/appui-react/tools/KeyinPaletteTools.tsx
	renamed:    ui/appui-react/src/appui-react/tools/OpenSettingsTool.ts -> ui/appui-react/src/appui-react/tools/OpenSettingsTool.tsx
	renamed:    ui/appui-react/src/appui-react/tools/RestoreLayoutTool.ts -> ui/appui-react/src/appui-react/tools/RestoreLayoutTool.tsx
	new file:   ui/appui-react/src/test/toolbar/ToolbarItemUtilities.test.tsx
	modified:   ui/imodel-components-react/src/imodel-components-react.ts
	new file:   ui/imodel-components-react/src/imodel-components-react/ToolUtilities.ts
	new file:   ui/imodel-components-react/src/test/ToolUtilities.test.tsx

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/changehistory/NextVersion.md
	both modified:   ui/appui-react/src/appui-react/toolbar/ToolbarItemUtilities.tsx

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