[backport#17162] chain: Remove CBlockIndex::SetNull helper
Summary:
fa0467326ff004a0a20c6af9c8f6adcc74a0c8af chain: Set all CBlockIndex members to null, remove SetNull helper (MarcoFalke)
Pull request description:
The first commit removes the `SetNull` helper and inlines the member initialization (C++11). See https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md#c-data-structures for rationale. <strike>The second commit adds the `cs_main` lock annotation to `RaiseValidity`. See also #17161.</strike>
Backport of Core PR17162
Test Plan:
ninja all check check-functional
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D8752