LibJS+LibWeb: Convert string view PrimitiveString instances to String

First, this adds an overload of PrimitiveString::create for StringView.
This overload will throw an OOM completion if creating a String fails.
This is not only a bit more convenient, but it also ensures at compile
time that all PrimitiveString::create(string_view) invocations will be
handled as String and OOM-aware.

Next, this wraps all invocations to PrimitiveString::create(string_view)
with MUST_OR_THROW_OOM.

A small PrimitiveString::create(DeprecatedFlyString) overload also had
to be added to disambiguate between the StringView and DeprecatedString
overloads.

Userland/Libraries/LibJS/Console.cpp

@@ -186,7 +186,7 @@ ThrowCompletionOr<Value> Console::assert_()
         return js_undefined();
 
     // 2. Let message be a string without any formatting specifiers indicating generically an assertion failure (such as "Assertion failed").
-    auto message = PrimitiveString::create(vm, "Assertion failed");
+    auto message = MUST_OR_THROW_OOM(PrimitiveString::create(vm, "Assertion failed"sv));
 
     // NOTE: Assemble `data` from the function arguments.
     MarkedVector<Value> data { vm.heap() };