Merge #15921: validation: Tidy up ValidationState interface

3004d5a12d [validation] Remove fMissingInputs from AcceptToMemoryPool() (John Newbery)
c428622a5b [validation] Remove unused first_invalid parameter from ProcessNewBlockHeaders() (John Newbery)
7204c6434b [validation] Remove useless ret parameter from Invalid() (John Newbery)
1a37de4b31 [validation] Remove error() calls from Invalid() calls (John Newbery)
067981e492 [validation] Tidy Up ValidationResult class (John Newbery)
a27a2957ed [validation] Add CValidationState subclasses (John Newbery)

Pull request description:

  Carries out some remaining tidy-ups remaining after PR 15141:

  - split ValidationState into TxValidationState and BlockValidationState (commit from ajtowns)
  - various minor code style tidy-ups to the ValidationState class
  - remove the useless `ret` parameter from `ValidationState::Invalid()`
  - remove the now unused `first_invalid` parameter from `ProcessNewBlockHeaders()`
  - remove the `fMissingInputs` parameter from `AcceptToMemoryPool()`, and deal with missing inputs the same way as other errors by using the `TxValidationState` object.

  Tip for reviewers (thanks ryanofsky!): The first commit ("[validation] Add CValidationState subclasses" ) is huge and can be easier to start reviewing if you revert the rote, mechanical changes:

  Substitute the commit hash of commit "[validation] Add CValidationState subclasses" for <CommitHash> in the commands below.

  ```sh
  git checkout <CommitHash>
  git grep -l ValidationState | xargs sed -i 's/BlockValidationState\|TxValidationState/CValidationState/g'
  git grep -l ValidationResult | xargs sed -i 's/BlockValidationResult\|TxValidationResult/ValidationInvalidReason/g'
  git grep -l MaybePunish | xargs sed -i 's/MaybePunishNode\(ForBlock\|ForTx\)/MaybePunishNode/g'
  git diff HEAD^
  ```

  After that it's possible to easily see the mechanical changes with:

  ```sh
  git log -p -n1 -U0 --word-diff-regex=. <CommitHash>
  ```

ACKs for top commit:
  laanwj:
    ACK 3004d5a12d
  amitiuttarwar:
    code review ACK 3004d5a12d. Also built & ran tests locally.
  fjahr:
    Code review ACK 3004d5a12d . Only nit style change and pure virtual destructor added since my last review.
  ryanofsky:
    Code review ACK 3004d5a12d. Just whitespace change and pure virtual destructor added since last review.

Tree-SHA512: 511de1fb380a18bec1944ea82b513b6192df632ee08bb16344a2df3c40811a88f3872f04df24bc93a41643c96c48f376a04551840fd804a961490d6c702c3d36

src/node/transaction.cpp

@@ -37,18 +37,16 @@ TransactionError BroadcastTransaction(NodeContext& node, const CTransactionRef t
     }
     if (!mempool.exists(hashTx)) {
         // Transaction is not already in the mempool. Submit it.
-        CValidationState state;
-        bool fMissingInputs;
-        if (!AcceptToMemoryPool(mempool, state, std::move(tx), &fMissingInputs,
+        TxValidationState state;
+        if (!AcceptToMemoryPool(mempool, state, std::move(tx),
                 nullptr /* plTxnReplaced */, false /* bypass_limits */, max_tx_fee)) {
+            err_string = FormatStateMessage(state);
             if (state.IsInvalid()) {
-                err_string = FormatStateMessage(state);
-                return TransactionError::MEMPOOL_REJECTED;
-            } else {
-                if (fMissingInputs) {
+                if (state.GetResult() == TxValidationResult::TX_MISSING_INPUTS) {
                     return TransactionError::MISSING_INPUTS;
                 }
-                err_string = FormatStateMessage(state);
+                return TransactionError::MEMPOOL_REJECTED;
+            } else {
                 return TransactionError::MEMPOOL_ERROR;
             }
         }