fix: QnA files multi-lang migration fix

[zhixzhan]

Description

Fix QnA files multi-lang migration failed, and some regression introduced by lazy indexing

Task Item

#minor

Screenshots

[coveralls]

Coverage increased (+0.006%) to 51.163% when pulling 50929a9 on zhixzhan/qna-migration-fix into 494d363 on main.

[liweitian]

If we have two languages, add qna pairs in dialogName.en-us.qna, will only generate dialogName-manual.source.en-us.qna. You can only generate dialogName-manual.source.qna, it will be copied to other languages on the second step of qna file migration.

And every dialogName.{locale}.qna files need to import the dialogName-manual.source.{locale}.qna.

[zhixzhan]

If we have two languages, add qna pairs in dialogName.en-us.qna, will only generate dialogName-manual.source.en-us.qna.
You can only generate dialogName-manual.source.qna, it will be copied to other languages on the second step of qna file migration.

@liweitian I think this is expected, because only in dialogName.en-us.qna have content to migrate, in other qna file dialogName.{locale}.qna there is nothing to migrate.

And every dialogName.{locale}.qna files need to import the dialogName-manual.source.{locale}.qna.

if there is not such file, there is no need to import it in every language.