refactor: Prepare for ParseHex -> ""_hex scripted-diff

- Adds using namespace.
- Extracts ToScript helper function from ScriptFromHex, to be used heavily in the next commit.
- Changes ScriptFromHex from using ParseHex to TryParseHex, now asserting the string is valid.
- Use even number of hex digits in comment (and apply replacement from next commit to only touch line once).

src/bench/index_blockfilter.cpp

@@ -25,6 +25,8 @@
 #include <memory>
 #include <vector>
 
+using namespace util::hex_literals;
+
 // Very simple block filter index sync benchmark, only using coinbase outputs.
 static void BlockFilterIndexSync(benchmark::Bench& bench)
 {

src/test/script_standard_tests.cpp

@@ -16,6 +16,7 @@
 
 #include <univalue.h>
 
+using namespace util::hex_literals;
 
 BOOST_FIXTURE_TEST_SUITE(script_standard_tests, BasicTestingSetup)
 

src/test/script_tests.cpp

@@ -1356,10 +1356,16 @@ BOOST_AUTO_TEST_CASE(script_GetScriptAsm)
     BOOST_CHECK_EQUAL(derSig + "83 " + pubKey, ScriptToAsmStr(CScript() << ToByteVector(ParseHex(derSig + "83")) << vchPubKey));
 }
 
+template <typename T>
+CScript ToScript(const T& byte_container)
+{
+    auto span{MakeUCharSpan(byte_container)};
+    return {span.begin(), span.end()};
+}
+
 static CScript ScriptFromHex(const std::string& str)
 {
-    std::vector<unsigned char> data = ParseHex(str);
+    return ToScript(*Assert(TryParseHex(str)));
-    return CScript(data.begin(), data.end());
 }
 
 BOOST_AUTO_TEST_CASE(script_FindAndDelete)
@@ -1393,7 +1399,7 @@ BOOST_AUTO_TEST_CASE(script_FindAndDelete)
     BOOST_CHECK_EQUAL(FindAndDelete(s, d), 1);
     BOOST_CHECK(s == expect);
 
-    s = ScriptFromHex("0302ff030302ff03"); // PUSH 0x2ff03 PUSH 0x2ff03
+    s = ToScript("0302ff030302ff03"_hex); // PUSH 0x02ff03 PUSH 0x02ff03
     d = ScriptFromHex("0302ff03");
     expect = CScript();
     BOOST_CHECK_EQUAL(FindAndDelete(s, d), 2);