Prioritize redundant packet checks

[expertdicer]

Closes: #817

Description

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• Added changelog entry, using unclog.
• Added tests.
• Linked to GitHub issue.
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[Farhad-Shabani]

Thank you @expertdicer for bringing up this issue.
I took another look at our checks and current logic and had a lightbulb moment. So, these new moves could boost the parallel relaying setup's performance, but there's a catch. We're kind of assuming that all relayers are on the up-and-up, just forwarding legit packets. But the thing is these changes (as we are placing basic checks afterward) leaves our implementation wide open to potential DOS attacks leaving us w/o having clues of why we are hitting these early no-op returns.
Apologies for that. I'll close the issue as well.