validation: replace ::Params() calls with chainstate/chainman member
refactor: Replace Chainstate::m_params with chainman.GetParams()
kernel: pass params to BlockManager rather than using a global
After these 3 commits, there is no more validation code using the global getter for the global CChainParams.
The chainparams are now accessed either:
- via a Config passed as a function argument
- via ChainstateManager::GetParams (uses ChainstateManager::m_config::GetChainParams())
- a chainparams function argument
This is a backport of core#25264, core#25830, core#24595