> consensus: don't call GetBlockPos in ReadBlockFromDisk without lock
The `cs_main` lock only covered the first invocation of `CBlockIndex::GetBlockPos()`.
Use the `blockPos` local variable instead of calling the function twice, rename it to `block_pos`, and make it const
This is a backport of core#22895
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> Require CBlockIndex::GetBlockPos() to hold mutex cs_main
This is a partial backport of core#22932
https://github.com/bitcoin/bitcoin/pull/22932/commits/6fd4341c10b319399c58d71c4ddeae4417e337d7