Merge #21055: [Bundle 3/n] Prune remaining g_chainman usage in validation functions

e11b649650 validation: CVerifyDB::VerifyDB: Use locking annotation (Carl Dong)
03f75c42e1 validation: Use existing chain member in CChainState::LoadGenesisBlock (Carl Dong)
5e4af77380 validation: Use existing chain member in CChainState::AcceptBlock (Carl Dong)
fee73347c0 validation: Pass in chain to FindBlockPos+SaveBlockToDisk (Carl Dong)
a9d28bcd8d validation: Use *this in CChainState::ActivateBestChainStep (Carl Dong)
4744efc9ba validation: Pass in chainstate to CTxMemPool::check (Carl Dong)
1fb7b2c595 validation: Use *this in CChainState::InvalidateBlock (Carl Dong)
8cdb2f7e58 validation: Move LoadBlockIndexDB to CChainState (Carl Dong)
8b99efbcc0 validation: Move invalid block handling to CChainState (Carl Dong)
2bdf37fe18 validation: Pass in chainstate to CVerifyDB::VerifyDB (Carl Dong)
31eac50c72 validation: Remove global ::VersionBitsTip{State,SinceHeight,Statistics} (Carl Dong)
63e4c7316a validation: Pass in chainstate to ::PruneBlockFilesManual (Carl Dong)
4bada76237 validation: Pass in chainstate to UpdateTip (Carl Dong)
a3ba08ba7d validation: Remove global ::{{Precious,Invalidate}Block,ResetBlockFailureFlags} (Carl Dong)
4927c9e699 validation: Remove global ::LoadGenesisBlock (Carl Dong)
9da106be4d validation: Check chain tip is non-null in CheckFinalTx (Carl Dong)

Pull request description:

  Overall PR: #20158 (tree-wide: De-globalize ChainstateManager)

  Based on:
  - [x] #20750 | [Bundle 2/n] Prune g_chainman usage in mempool-related validation functions

  Note to reviewers:
  1. This bundle may _apparently_ introduce usage of `g_chainman` or `::Chain(state|)Active()` globals, but these are resolved later on in the overall PR. [Commits of overall PR](https://github.com/bitcoin/bitcoin/pull/20158/commits)
  2. There may be seemingly obvious local references to `ChainstateManager` or other validation objects which are not being used in callers of the current function in question, this is done intentionally to **_keep each commit centered around one function/method_** to ease review and to make the overall change systematic. We don't assume anything about our callers. Rest assured that once we are considering that particular caller in later commits, we will use the obvious local references. [Commits of overall PR](https://github.com/bitcoin/bitcoin/pull/20158/commits)
  3. When changing a function/method that has many callers (e.g. `LookupBlockIndex` with 55 callers), it is sometimes easier (and less error-prone) to use a scripted-diff. When doing so, there will be 3 commits in sequence so that every commit compiles like so:
  1. Add `new_function`, make `old_function` a wrapper of `new_function`, divert all calls to `old_function` to `new_function` **in the local module only**
  2. Scripted-diff to divert all calls to `old_function` to `new_function` **in the rest of the codebase**
  3. Remove `old_function`

  Note to self:
  - [x] Address: https://github.com/bitcoin/bitcoin/pull/20750#discussion_r579400663

ACKs for top commit:
  laanwj:
    Code review ACK e11b649650

Tree-SHA512: 205a451a741e32f17d5966de289f2f5a3f0817738c0087b70ff4755ddd217b53d01050ed396669bda2b1d216a88d927b9778777f9ff95ab1fe20e59c5f341776

src/init.cpp

@@ -720,7 +720,7 @@ static void ThreadImport(ChainstateManager& chainman, std::vector<fs::path> vImp
         fReindex = false;
         LogPrintf("Reindexing finished\n");
         // To avoid ending up in a situation without genesis block, re-try initializing (no-op if reindexing worked):
-        LoadGenesisBlock(chainparams);
+        ::ChainstateActive().LoadGenesisBlock(chainparams);
     }
 
     // -loadblock=
@@ -1636,7 +1636,7 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
                 // If we're not mid-reindex (based on disk + args), add a genesis block on disk
                 // (otherwise we use the one already on disk).
                 // This is called again in ThreadImport after the reindex completes.
-                if (!fReindex && !LoadGenesisBlock(chainparams)) {
+                if (!fReindex && !::ChainstateActive().LoadGenesisBlock(chainparams)) {
                     strLoadError = _("Error initializing block database");
                     break;
                 }
@@ -1747,7 +1747,7 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
                         // work when we allow VerifyDB to be parameterized by chainstate.
                         if (&::ChainstateActive() == chainstate &&
                             !CVerifyDB().VerifyDB(
-                                chainparams, &chainstate->CoinsDB(),
+                                chainparams, *chainstate, &chainstate->CoinsDB(),
                                 args.GetArg("-checklevel", DEFAULT_CHECKLEVEL),
                                 args.GetArg("-checkblocks", DEFAULT_CHECKBLOCKS))) {
                             strLoadError = _("Corrupted block database detected");