scripted-diff: modernize outdated trait patterns - values

See https://en.cppreference.com/w/cpp/types/is_enum for more details.

-BEGIN VERIFY SCRIPT-
sed -i -E 's/(std::[a-z_]+)(<[^<>]+>)::value\b/\1_v\2/g' $(git grep -l '::value' ./src ':(exclude)src/bench/nanobench.h' ':(exclude)src/minisketch' ':(exclude)src/span.h')
-END VERIFY SCRIPT-

src/test/fuzz/integer.cpp

@@ -63,7 +63,7 @@ FUZZ_TARGET(integer, .init = initialize_integer)
     const int16_t i16 = fuzzed_data_provider.ConsumeIntegral<int16_t>();
     const uint8_t u8 = fuzzed_data_provider.ConsumeIntegral<uint8_t>();
     const int8_t i8 = fuzzed_data_provider.ConsumeIntegral<int8_t>();
-    // We cannot assume a specific value of std::is_signed<char>::value:
+    // We cannot assume a specific value of std::is_signed_v<char>:
     // ConsumeIntegral<char>() instead of casting from {u,}int8_t.
     const char ch = fuzzed_data_provider.ConsumeIntegral<char>();
     const bool b = fuzzed_data_provider.ConsumeBool();