eth/tracers: add support for block overrides in debug_traceCall (#24871)

This PR adds support for block overrides when doing debug_traceCall.

- Previously, debug_traceCall against pending erroneously used a common.Hash{} stateroot when looking up the state, meaning that a totally empty state was used -- so it always failed,
- With this change, we reject executing debug_traceCall against pending.
- And we add ability to override all evm-visible header fields.

internal/ethapi/api.go

@@ -888,6 +888,41 @@ func (diff *StateOverride) Apply(state *state.StateDB) error {
 	return nil
 }
 
+// BlockOverrides is a set of header fields to override.
+type BlockOverrides struct {
+	Number     *hexutil.Big
+	Difficulty *hexutil.Big
+	Time       *hexutil.Big
+	GasLimit   *hexutil.Uint64
+	Coinbase   *common.Address
+	Random     *common.Hash
+}
+
+// Apply overrides the given header fields into the given block context.
+func (diff *BlockOverrides) Apply(blockCtx *vm.BlockContext) {
+	if diff == nil {
+		return
+	}
+	if diff.Number != nil {
+		blockCtx.BlockNumber = diff.Number.ToInt()
+	}
+	if diff.Difficulty != nil {
+		blockCtx.Difficulty = diff.Difficulty.ToInt()
+	}
+	if diff.Time != nil {
+		blockCtx.Time = diff.Time.ToInt()
+	}
+	if diff.GasLimit != nil {
+		blockCtx.GasLimit = uint64(*diff.GasLimit)
+	}
+	if diff.Coinbase != nil {
+		blockCtx.Coinbase = *diff.Coinbase
+	}
+	if diff.Random != nil {
+		blockCtx.Random = diff.Random
+	}
+}
+
 func DoCall(ctx context.Context, b Backend, args TransactionArgs, blockNrOrHash rpc.BlockNumberOrHash, overrides *StateOverride, timeout time.Duration, globalGasCap uint64) (*core.ExecutionResult, error) {
 	defer func(start time.Time) { log.Debug("Executing EVM call finished", "runtime", time.Since(start)) }(time.Now())