A full TestingSetup is required for both coins_view and
load_external_block_file as they interact with the active chainstate.
This is a backport of [[https://github.com/bitcoin/bitcoin/pull/20946 | core#20946]] [2/2]
https://github.com/bitcoin/bitcoin/pull/20946/commits/abb6fa728598c4cc8874eae1c3c5e587e36424cd
Depends on D11678