refactor: replace DataStream with SpanReader in block deserialization tests

These benchmark inputs are immutable fixture bytes, so `DataStream` adds an unnecessary owned buffer and the setup needed to recreate or preserve its state.

Use `SpanReader` for block deserialization in `checkblock` instead.
This keeps `DeserializeBlockTest` focused on deserialization work, while `CheckBlockTest` still uses untimed setup only to rebuild a fresh uncached `CBlock` for the timed `CheckBlock()` call.

Co-authored-by: MarcoFalke <*~=`'#}+{/-|&$^_@721217.xyz>

src/bench/checkblock.cpp

@@ -4,22 +4,14 @@
 
 #include <bench/bench.h>
 #include <bench/data/block413567.raw.h>
-#include <chainparams.h>
-#include <common/args.h>
 #include <consensus/validation.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
-#include <serialize.h>
-#include <span.h>
 #include <streams.h>
-#include <util/chaintype.h>
 #include <validation.h>
 
 #include <cassert>
 #include <cstddef>
-#include <memory>
-#include <optional>
-#include <vector>
 
 // These are the two major time-sinks which happen after we have fully received
 // a block off the wire, but before we can relay the block on to peers using
@@ -27,27 +19,29 @@
 
 static void DeserializeBlockTest(benchmark::Bench& bench)
 {
-    DataStream stream;
-    bench.unit("block").epochIterations(1)
-        .setup([&] { stream = DataStream{benchmark::data::block413567}; })
-        .run([&] { CBlock block; stream >> TX_WITH_WITNESS(block); });
+    const auto block_data{benchmark::data::block413567};
+    bench.unit("block").run([&] {
+        CBlock block;
+        SpanReader{block_data} >> TX_WITH_WITNESS(block);
+        assert(block.vtx.size() == 1557);
+    });
 }
 
 static void CheckBlockTest(benchmark::Bench& bench)
 {
-    ArgsManager bench_args;
-    const auto chainParams = CreateChainParams(bench_args, ChainType::MAIN);
+    const auto& chain_params{CChainParams::Main()};
+    const auto block_data{benchmark::data::block413567};
 
     CBlock block;
     bench.unit("block").epochIterations(1)
         .setup([&] {
             block = CBlock{};
-            DataStream stream{benchmark::data::block413567};
-            stream >> TX_WITH_WITNESS(block);
+            SpanReader{block_data} >> TX_WITH_WITNESS(block);
+            assert(block.vtx.size() == 1557);
         })
         .run([&] {
             BlockValidationState validationState;
-            bool checked = CheckBlock(block, validationState, chainParams->GetConsensus());
+            const bool checked{CheckBlock(block, validationState, chain_params->GetConsensus())};
             assert(checked);
         });
 }