[[https://github.com/bitcoin/bitcoin/pull/14822/files | PR14822]] backport
fa5cef0f78 bench: Destroy wallet txs instead of leaking their memory (MarcoFalke)
Pull request description:
This should destroy the wallet txs when the benchmark ends to avoid having to hold them when the following benchmarks run.
Depends on D5251 (only for having updated valgrind suppressions, besides this it is landable anytime)