Merge #18641: test: Create cached blocks not in the future

Summary:
fa320975411af4f0e41771d89958a77fd7a2284b test: Create cached blocks not in the future (MarcoFalke)

Pull request description:

This avoids test failures when tests assume blocks are not from the future, like in wallet_dump: https://cirrus-ci.com/task/6607130193035264?command=ci#L3306

ACKs for top commit:

jonatack:
  ACK fa320975411af4f0e41771d89958a77fd7a2284b

Tree-SHA512: 60b6882e0e1df8c5d67f034533407a45d3685983891b67ff4631072bfd0a93a325c7ca18758d7a2df252e4fcdb7c87321cb1e84458b22782e57e719eec634c22

Backport of Core PR18641

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, nakihito

Reviewed By: nakihito

Differential Revision: https://reviews.bitcoinabc.org/D6071