Extract out the inventory logging to a lambda
Extract out the inventory logging to a lambda

Summary:
This is a little deduplication that can be leveraged when introducing
proofs inventories.

Test Plan:
  ninja all check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D9590

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