PartitionAlloc: Centralize Partition allocators into one place (Part 1)

Source/wtf/wtf.gypi

 # For GN compatibility, this file can not have any conditions.
 {
     'variables': {
         'wtf_files': [
             'ASCIICType.h',
             'AddressSpaceRandomization.cpp',
             'AddressSpaceRandomization.h',
             'Alignment.h',
             'ArrayBuffer.cpp',
             'ArrayBuffer.h',
@@ skipping 73 matching lines @@
             'NonCopyingSort.h',
             'Noncopyable.h',
             'NotFound.h',
             'NullPtr.h',
             'OwnPtr.h',
             'OwnPtrCommon.h',
             'PageAllocator.cpp',
             'PageAllocator.h',
             'PartitionAlloc.cpp',
             'PartitionAlloc.h',
+            'Partitions.cpp',
+            'Partitions.h',
             'PassOwnPtr.h',
             'PassRefPtr.h',
             'PassTraits.h',
             'PrintStream.cpp',
             'PrintStream.h',
             'ProcessID.h',
             'RefCounted.h',
             'RefCountedLeakCounter.cpp',
             'RefCountedLeakCounter.h',
             'RefPtr.h',
@@ skipping 129 matching lines @@
             'text/TextCodecUTF8Test.cpp',
             'text/WTFStringTest.cpp',
         ],
         'wtf_unittest_helper_files': [
             'testing/WTFTestHelpers.cpp',
             'testing/WTFTestHelpers.h',
             'testing/WTFUnitTestHelpersExport.h',
         ],
     },
 }