Log when an import is being skipped because we already have it
Log when an import is being skipped because we already have it

Summary:
Behavior Changes:
* Those pubkeys being imported with add_keypool set and are already in the wallet will no longer be added to the keypool

This is a partial backport of Core [[https://github.com/bitcoin/bitcoin/pull/16301 | PR16301]] : https://github.com/bitcoin/bitcoin/pull/16301/commits/fae7a5befd0b8746d84a6fde575e5b4ea46cb3c4

Test Plan:
  ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D6411

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