LibJS: Pass Interpreter& to Value::to_number() et al.

This patch is unfortunately rather large and might make some things feel
bloated, but it is necessary to fix a few flaws in LibJS, primarily
blindly coercing values to numbers without exception checks - i.e.

interpreter.argument(0).to_i32();  // can fail!!!

Some examples where the interpreter would actually crash:

var o = { toString: () => { throw Error() } };
+o;
o - 1;
"foo".charAt(o);
"bar".repeat(o);

To fix this, we now have the following...

to_double(Interpreter&)
to_i32()
to_i32(Interpreter&)
to_size_t()
to_size_t(Interpreter&)

...and a whole lot of exception checking.

There's intentionally no to_double(), use as_double() directly instead.

This way we still can use these convenient utility functions but don't
need to check for exceptions if we are sure the value already is a
number.

Fixes #2267.

Userland/js.cpp

@@ -328,9 +328,10 @@ JS::Value ReplObject::exit_interpreter(JS::Interpreter& interpreter)
 {
     if (!interpreter.argument_count())
         exit(0);
-    int exit_code = interpreter.argument(0).to_number().as_double();
-    exit(exit_code);
-    return JS::js_undefined();
+    auto exit_code = interpreter.argument(0).to_number(interpreter);
+    if (interpreter.exception())
+        return {};
+    exit(exit_code.as_double());
 }
 
 JS::Value ReplObject::repl_help(JS::Interpreter&)