LibJS: Replace GlobalObject with VM in Intl AOs [Part 1/19]

Instead of passing a GlobalObject everywhere, we will simply pass a VM,
from which we can get everything we need: common names, the current
realm, symbols, arguments, the heap, and a few other things.

In some places we already don't actually need a global object and just
do it for consistency - no more `auto& vm = global_object.vm();`!

This will eventually automatically fix the "wrong realm" issue we have
in some places where we (incorrectly) use the global object from the
allocating object, e.g. in call() / construct() implementations. When
only ever a VM is passed around, this issue can't happen :^)

I've decided to split this change into a series of patches that should
keep each commit down do a somewhat manageable size.

Userland/Libraries/LibJS/Runtime/Intl/DateTimeFormatFunction.cpp

@@ -58,7 +58,7 @@ ThrowCompletionOr<Value> DateTimeFormatFunction::call()
     }
 
     // 5. Return ? FormatDateTime(dtf, x).
-    auto formatted = TRY(format_date_time(global_object, m_date_time_format, date_value));
+    auto formatted = TRY(format_date_time(vm, m_date_time_format, date_value));
     return js_string(vm, move(formatted));
 }