DevTools+LibJS+LibWeb: Change class_name to use StringView

This helps make the overall codebase consistent. `class_name()` in
`Kernel` is always `StringView`, but not elsewhere.

Additionally, this results in the `strlen` (which needs to be done
when printing or other operations) always being computed at
compile-time.

Userland/Libraries/LibJS/Runtime/BigInt.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/StringView.h>
 #include <LibCrypto/BigInt/SignedBigInteger.h>
 #include <LibJS/Heap/Cell.h>
 
@@ -20,7 +21,7 @@ public:
     const String to_string() const { return String::formatted("{}n", m_big_integer.to_base(10)); }
 
 private:
-    virtual const char* class_name() const override { return "BigInt"; }
+    virtual StringView class_name() const override { return "BigInt"sv; }
 
     Crypto::SignedBigInteger m_big_integer;
 };