Add linkDomain support for ActionCodeSettting. This will generate Hosting-formatted email link.

[Xiaoshouzi-gh]

including error codes and sample app change

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[google-oss-bot]

	1 Warning
:warning:	Did you forget to add a changelog entry? (Add #no-changelog to the PR description to silence this warning.)

Generated by :no_entry_sign: Danger

[paulb777]

Closing since linkDomain was merged from #14384