This is a reland of 6c68efac

Updated Heap::CommittedMemory and related functions to iterate over all
spaces rather than including them manually which can lead to a space
being overlooked. Also adds a test to ensure this the case.

Original change's description:
> Revert "Reland "[heap] Move initial objects into RO_SPACE""
>
> This reverts commit 6c68efac.
>
> Reason for revert: https://bugs.chromium.org/p/v8/issues/detail?id=7668
>
> Original change's description:
> > Reland "[heap] Move initial objects into RO_SPACE"
> >
> > This is a reland of f8ae62fe
> >
> > Original change's description:
> > > [heap] Move initial objects into RO_SPACE
> > >
> > > 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}
> >
> > Bug: v8:7464
> > Change-Id: I50427edfeb53ca80ec4cf46566368fb2213ccf7b
> > Reviewed-on: https://chromium-review.googlesource.com/999654
> > Commit-Queue: Dan Elphick <delphick@chromium.org>
> > Reviewed-by: Yang Guo <yangguo@chromium.org>
> > Reviewed-by: Hannes Payer <hpayer@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#52638}
>
> TBR=rmcilroy@chromium.org,yangguo@chromium.org,hpayer@chromium.org,mlippautz@chromium.org,delphick@chromium.org
>
> # Not skipping CQ checks because original CL landed > 1 day ago.
>
> Bug: v8:7464,v8:7668
> Change-Id: I10aa03623b51e997f95a3715ea9f0bf5d29d2cdb
> Reviewed-on: https://chromium-review.googlesource.com/1016600
> Commit-Queue: Peter Marshall <petermarshall@chromium.org>
> Reviewed-by: Peter Marshall <petermarshall@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#52667}

Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: If4b7490c8c4d31612de8ec132de334955a319b11
Bug: v8:7464, v8:7668
Reviewed-on: https://chromium-review.googlesource.com/1019020Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52689}