Have importpubkey use CWallet's ImportScriptPubKeys and ImportPubKeys functions

Summary:
Behavior changes:

• If any scripts for the pubkey were already in the wallet, their timestamps will be set to 1 and label updated

This is a partial backport of Core PR16301 : https://github.com/bitcoin/bitcoin/pull/16301/commits/a00d1e5ec5eb019f8bbeb060a2b09e341d360fe5

Depends on D6410

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D6413