Add descriptor expansion cache

Summary:
This is a partial backport of Core PR14646 : https://github.com/bitcoin/bitcoin/pull/14646/commits/82df4c64ffa2f0dd45e7ae694903615358f121a6

Depends on D6196

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D6197