Adds a new field rare_data of type FunctionTemplateRareData to
FunctionTemplateInfo and moves 8 others which are unset on 90% of
FunctionTemplateInfo objects to this field.

Getters like prototype_template() are changed to GetPrototypeTemplate()
to indicate they're not trivial. The setters are replaced with static
methods (e.g. SetPrototypeTemplate) that take an Isolate and the
template object, since they can now perform allocation.

Bug: v8:8478
Change-Id: If72b132ade4ca4a3f803f913761c9caddc0e9dd6
Reviewed-on: https://chromium-review.googlesource.com/c/1342519
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57725}