test: Speed up rpc_blockchain.py by removing miniwallet.generate()
Summary:
Speed up various tests:
Remove unused nodes, which only consume time on start/stop
Remove unused "bug workarounds"
Remove the need for miniwallet.generate() by adding miniwallet.scan_blocks(). (On my system, with valgrind, generating 105 blocks takes 3.31 seconds. Rescanning 5 blocks takes 0.11 seconds.)Backport of core#21200.
Test Plan:
ninja all check-all
Reviewers: #bitcoin_abc, sdulfari
Reviewed By: #bitcoin_abc, sdulfari
Differential Revision: https://reviews.bitcoinabc.org/D12432