Have importaddress use ImportScripts and ImportScriptPubKeys

Summary:
Also removes the now unused ImportAddress and ImportScript from rpcdump.cpp

Behavior changes:

• No errors will be thrown when the script or key already exists in the wallet.
• If the key or script is already in the wallet, their labels will be updated.

This is a partial backport of Core PR16301 : https://github.com/bitcoin/bitcoin/pull/16301/commits/94bf156f391759420465b2ff8c44f5f150246c7f

Depends on D6413

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D6414