However, keep a declaration in validation to make it possible to move
smaller chunks to blockstorage without breaking compilation.
Also, expose AbortNode in the header.
Can be reviewed with --color-moved=dimmed-zebra --color-moved-ws=ignore-all-space
This is a backport of core#21727 [2/4]
https://github.com/bitcoin/bitcoin/pull/21727/commits/fa247a327fc7c7cea6bc8f93637b8babd3015ffa
Depends on D12032