Add a way to route different issues to different email lists

## Background
Currently, Pramen supports only 2 email lists - one for successes, and one for failures.

Sometimes, depending on an error, for example, emails can be routed to different teams.

This can be part of a pluggable component to decide which email list to send emails to.

This is already supported for other notification types via pipeline notification targets.

## Feature
Add a way to route different issues to different email lists.

## Example [Optional]
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## Proposed Solution [Optional]
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