This moves:
* the main oddballs (null, undefined, hole, true, false) as well as
their supporting maps (also adds hole as an internalized string to make
this work).
* most of the internalized strings
* the struct maps
* empty array
* empty enum cache
* the contents of the initial string table
* the weak_cell_cache for any map in RO_SPACE (and eagerly creates the
value avoid writing to it during run-time)

The StartupSerializer stats change as follows:

     RO_SPACE  NEW_SPACE  OLD_SPACE  CODE_SPACE  MAP_SPACE  LO_SPACE
old         0          0     270264       32608      12144         0
new     21776          0     253168       32608       8184         0
Overall memory usage has increased by 720 bytes due to the eager
initialization of the Map weak cell caches.

Also extends --serialization-statistics to print out separate instance
type stats for objects in RO_SPACE as shown here:

  Read Only Instance types (count and bytes):
       404      16736  ONE_BYTE_INTERNALIZED_STRING_TYPE
         2         32  HEAP_NUMBER_TYPE
         5        240  ODDBALL_TYPE
        45       3960  MAP_TYPE
         1         16  BYTE_ARRAY_TYPE
         1         24  TUPLE2_TYPE
         1         16  FIXED_ARRAY_TYPE
         1         32  DESCRIPTOR_ARRAY_TYPE
        45        720  WEAK_CELL_TYPE

Bug: v8:7464
Change-Id: I12981c39c82a7057f68bbbe03f89fb57b0b4c6a6
Reviewed-on: https://chromium-review.googlesource.com/973722
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52435}