bench: Add block assemble benchmark

Summary: This is a backport of Core PR13219 and PR13806 . Due to many backport being done out of oder or improperly, this contains elements of PR15413 and PR15788

Test Plan:

make check
./src/bench/bench_bitcoin

Check that the new benchmark is run.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D5848