ColorDef validation and ColorByName fix (backport #3360)

[mergify]

This is an automatic backport of pull request #3360 done by Mergify.
Cherry-pick of 84290b9 has failed:

On branch mergify/bp/release/2.19.x/pr-3360
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You are currently cherry-picking commit 84290b9c58.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   common/api/imodeljs-common.api.md
	modified:   common/api/summary/imodeljs-common.exports.csv
	new file:   common/changes/@itwin/core-common/pmc-validate-color-def_2022-03-15-15-16.json
	new file:   common/changes/@itwin/imodel-components-react/pmc-validate-color-def_2022-03-15-16-52.json
	modified:   core/common/src/test/ColorDef.test.ts
	modified:   test-apps/ui-test-extension/src/ui/tools/SampleTool.ts
	modified:   ui/components/src/test/TestUtils.ts

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   core/common/src/ColorByName.ts
	both modified:   core/common/src/ColorDef.ts
	both modified:   docs/changehistory/NextVersion.md
	deleted by us:   test-apps/ui-items-providers-test/src/ui/dialogs/TestUiProviderDialog.ts
	both modified:   test-apps/ui-test-app/src/frontend/appui/dialogs/TestUiProviderDialog.ts
	both modified:   ui/components/src/test/color/ColorPickerButton.test.tsx
	both modified:   ui/components/src/test/color/ColorPickerDialog.test.tsx
	both modified:   ui/components/src/test/editors/ColorEditor.test.tsx
	deleted by us:   ui/imodel-components-react/src/test/color/ColorPickerPopup.test.tsx

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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