message: validation: use stronger EXCLUSIVE_LOCKS_REQUIRED()
  added annotations to
  denote that the callers of `CChainState::ActivateBestChain()` and
  `CChainState::InvalidateBlock()` must not own `m_chainstate_mutex` at
  the time of the call.
  Replace the added `LOCKS_EXCLUDED()` with a stronger
  `EXCLUSIVE_LOCKS_REQUIRED()`, see
  for the
  difference between both.
diff: @@ -595,7 +595,8 @@ public:
  EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
  /** Import blocks from an external file */
  - void LoadExternalBlockFile(FILE* fileIn, FlatFilePos* dbp = nullptr);
  + void LoadExternalBlockFile(FILE* fileIn, FlatFilePos* dbp = nullptr)
  + EXCLUSIVE_LOCKS_REQUIRED(!m_chainstate_mutex);
  /**
  * Update the on-disk chain state.
  @@ -637,7 +638,9 @@ public:
  */
  bool ActivateBestChain(
  BlockValidationState& state,
  - std::shared_ptr<const CBlock> pblock = nullptr) LOCKS_EXCLUDED(m_chainstate_mutex, cs_main);
  + std::shared_ptr<const CBlock> pblock = nullptr)
  + EXCLUSIVE_LOCKS_REQUIRED(!m_chainstate_mutex)
  + LOCKS_EXCLUDED(::cs_main);
  bool AcceptBlock(const std::shared_ptr<const CBlock>& pblock, BlockValidationState& state, CBlockIndex** ppindex, bool fRequested, const FlatFilePos* dbp, bool* fNewBlock) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  @@ -655,9 +658,15 @@ public:
  *
  * May not be called in a validationinterface callback.
  */
  - bool PreciousBlock(BlockValidationState& state, CBlockIndex* pindex) LOCKS_EXCLUDED(cs_main);
  + bool PreciousBlock(BlockValidationState& state, CBlockIndex* pindex)
  + EXCLUSIVE_LOCKS_REQUIRED(!m_chainstate_mutex)
  + LOCKS_EXCLUDED(::cs_main);
  +
  /** Mark a block as invalid. */
  - bool InvalidateBlock(BlockValidationState& state, CBlockIndex* pindex) LOCKS_EXCLUDED(m_chainstate_mutex, cs_main);
  + bool InvalidateBlock(BlockValidationState& state, CBlockIndex* pindex)
  + EXCLUSIVE_LOCKS_REQUIRED(!m_chainstate_mutex)
  + LOCKS_EXCLUDED(::cs_main);
  +
  /** Remove invalidity status from a block and its descendants. */
  void ResetBlockFailureFlags(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  