LibJS+LibWeb: Use realm.create<T> instead of heap.allocate<T>

The main motivation behind this is to remove JS specifics of the Realm
from the implementation of the Heap.

As a side effect of this change, this is a bit nicer to read than the
previous approach, and in my opinion, also makes it a little more clear
that this method is specific to a JavaScript Realm.

Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp

@@ -15,7 +15,7 @@ JS_DEFINE_ALLOCATOR(CollatorCompareFunction);
 
 NonnullGCPtr<CollatorCompareFunction> CollatorCompareFunction::create(Realm& realm, Collator& collator)
 {
-    return realm.heap().allocate<CollatorCompareFunction>(realm, realm, collator);
+    return realm.create<CollatorCompareFunction>(realm, collator);
 }
 
 CollatorCompareFunction::CollatorCompareFunction(Realm& realm, Collator& collator)

Libraries/LibJS/Runtime/Intl/DateTimeFormatFunction.cpp

@@ -19,7 +19,7 @@ JS_DEFINE_ALLOCATOR(DateTimeFormatFunction);
 // 11.5.4 DateTime Format Functions, https://tc39.es/ecma402/#sec-datetime-format-functions
 NonnullGCPtr<DateTimeFormatFunction> DateTimeFormatFunction::create(Realm& realm, DateTimeFormat& date_time_format)
 {
-    return realm.heap().allocate<DateTimeFormatFunction>(realm, date_time_format, realm.intrinsics().function_prototype());
+    return realm.create<DateTimeFormatFunction>(date_time_format, realm.intrinsics().function_prototype());
 }
 
 DateTimeFormatFunction::DateTimeFormatFunction(DateTimeFormat& date_time_format, Object& prototype)

Libraries/LibJS/Runtime/Intl/Locale.cpp

@@ -19,7 +19,7 @@ JS_DEFINE_ALLOCATOR(Locale);
 
 NonnullGCPtr<Locale> Locale::create(Realm& realm, NonnullGCPtr<Locale> source_locale, String locale_tag)
 {
-    auto locale = realm.heap().allocate<Locale>(realm, realm.intrinsics().intl_locale_prototype());
+    auto locale = realm.create<Locale>(realm.intrinsics().intl_locale_prototype());
 
     locale->set_locale(move(locale_tag));
     locale->m_calendar = source_locale->m_calendar;

Libraries/LibJS/Runtime/Intl/NumberFormatFunction.cpp

@@ -15,7 +15,7 @@ JS_DEFINE_ALLOCATOR(NumberFormatFunction);
 // 15.5.2 Number Format Functions, https://tc39.es/ecma402/#sec-number-format-functions
 NonnullGCPtr<NumberFormatFunction> NumberFormatFunction::create(Realm& realm, NumberFormat& number_format)
 {
-    return realm.heap().allocate<NumberFormatFunction>(realm, number_format, realm.intrinsics().function_prototype());
+    return realm.create<NumberFormatFunction>(number_format, realm.intrinsics().function_prototype());
 }
 
 NumberFormatFunction::NumberFormatFunction(NumberFormat& number_format, Object& prototype)

Libraries/LibJS/Runtime/Intl/SegmentIterator.cpp

@@ -21,7 +21,7 @@ NonnullGCPtr<SegmentIterator> SegmentIterator::create(Realm& realm, Unicode::Seg
     // 4. Set iterator.[[IteratedString]] to string.
     // 5. Set iterator.[[IteratedStringNextSegmentCodeUnitIndex]] to 0.
     // 6. Return iterator.
-    return realm.heap().allocate<SegmentIterator>(realm, realm, segmenter, string, segments);
+    return realm.create<SegmentIterator>(realm, segmenter, string, segments);
 }
 
 // 18.6 Segment Iterator Objects, https://tc39.es/ecma402/#sec-segment-iterator-objects

Libraries/LibJS/Runtime/Intl/Segments.cpp

@@ -20,7 +20,7 @@ NonnullGCPtr<Segments> Segments::create(Realm& realm, Unicode::Segmenter const&
     // 3. Set segments.[[SegmentsSegmenter]] to segmenter.
     // 4. Set segments.[[SegmentsString]] to string.
     // 5. Return segments.
-    return realm.heap().allocate<Segments>(realm, realm, segmenter, move(string));
+    return realm.create<Segments>(realm, segmenter, move(string));
 }
 
 // 18.5 Segments Objects, https://tc39.es/ecma402/#sec-segments-objects