Needinfo triage owners for release-tracked (tracking-firefoxNNN+) bugs without severity/priority

[gijsk]

CC @rvandermeulen

Proposed template text for the needinfo:

This bug is marked as tracked for {FirefoxNNN (nightly/beta/release/esr)}. As the triage owner, could you set the severity field, and if appropriate find an assignee and assign a priority? If you believe this bug is not very severe and shouldn't be tracked for this release, please explain why and needinfo {releaseowner}

[gijsk]

Alternatively, we could be more assertive and mark it as S2 ourselves and still needinfo, and replace the "could you set the severity field" bit with "Because the bug is tracked we have set severity to S2; please increment to S1 if needed. If this doesn't warrant S2 and tracking, please explain why and needinfo {releaseowner}." or similar