Chore: encapsulate external issues list resolver

What does this MR do and why?

Reason

For upcoming Ones integrations: #365123 (closed)

Since Ones integration is basically identical to ZenTao, so I think we should extract the duplicated code out in advance to prevent code duplication.

/cc @prajnamas @orozot @qk44077907

Note

This is only intended for Ones and ZenTao integration.

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