[backport#16743] refactor: move LoadChainTip/RelayBlocks under CChainState
3cf36736e540cf06250701f0934a7946836d000d refactoring: move ReplayBlocks under CChainState (James O'Beirne)
bcf73d3b84649c8786f0cccc6862dd1bbdb9950b refactoring: move LoadChainTip to CChainState method (James O'Beirne)
f5809d5b135c7f9de5217d3cda76638fe7eed58a doc: fix CChainState::ActivateBestChain doc (James O'Beirne)
Pull request description:
This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11): Parent PR: #15606 Issue: #15605 Specification: https://github.com/jamesob/assumeutxo-docs/tree/master/proposal --- Move more chainstate-related functionality to methods on CChainState. Nothing too interesting here, but needed to work with multiple chainstates. And brief to review. :) Also fixes doc on ActivateBestChain.
ACKs for top commit:
MarcoFalke: ACK 3cf36736e540cf06250701f0934a7946836d000d ryanofsky: Can confirm. utACK 3cf36736e540cf06250701f0934a7946836d000d. Removes wrapper functions and removes more ::ChainActive() and ::ChainstateActive() calls than it adds, so seems good.
Backport of Core PR16743
ninja all check check-functional
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D7960