Add benchmark for TryParseHex

Running `make && ./src/bench/bench_bitcoin -filter=HexParse` a few times results in:
```
|           ns/base16 |            base16/s |    err% |     total | benchmark
|--------------------:|--------------------:|--------:|----------:|:----------
|                1.60 |      623,238,893.11 |    0.3% |      0.01 | `HexParse`
|                1.65 |      606,747,566.34 |    0.6% |      0.01 | `HexParse`
|                1.60 |      626,149,544.07 |    0.3% |      0.01 | `HexParse`
```

src/Makefile.bench.include

@@ -42,6 +42,7 @@ bench_bench_bitcoin_SOURCES = \
   bench/merkle_root.cpp \
   bench/nanobench.cpp \
   bench/nanobench.h \
+  bench/parse_hex.cpp \
   bench/peer_eviction.cpp \
   bench/poly1305.cpp \
   bench/pool.cpp \

src/bench/parse_hex.cpp

@@ -0,0 +1,36 @@
+// Copyright (c) 2024- The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <bench/bench.h>
+#include <random.h>
+#include <stddef.h>
+#include <util/strencodings.h>
+#include <cassert>
+#include <optional>
+#include <vector>
+
+std::string generateHexString(size_t length) {
+    const auto hex_digits = "0123456789ABCDEF";
+    FastRandomContext rng(/*fDeterministic=*/true);
+
+    std::string data;
+    while (data.size() < length) {
+        auto digit = hex_digits[rng.randbits(4)];
+        data.push_back(digit);
+    }
+    return data;
+}
+
+static void HexParse(benchmark::Bench& bench)
+{
+    auto data = generateHexString(130); // Generates 678B0EDA0A1FD30904D5A65E3568DB82DB2D918B0AD8DEA18A63FECCB877D07CAD1495C7157584D877420EF38B8DA473A6348B4F51811AC13C786B962BEE5668F9 by default
+
+    bench.batch(data.size()).unit("base16").run([&] {
+        auto result = TryParseHex(data);
+        assert(result != std::nullopt); // make sure we're measuring the successful case
+        ankerl::nanobench::doNotOptimizeAway(result);
+    });
+}
+
+BENCHMARK(HexParse, benchmark::PriorityLevel::HIGH);