Currently each isolate stores its own array of
{CallInterfaceDescriptorData}. This array has size 173, and each entry
has 40 bytes. That's already 7kB per isolate.
Additionally, each {CallInterfaceDescriptorData} allocates two
heap-allocated arrays, which probably add up to more than the static
size of the {CallInterfaceDescriptorData}. Note that all the
{CallInterfaceDescriptorData} instances are initialized eagerly on
isolate creation.

Since {CallInterfaceDescriptor} is totally isolate independent itself,
this CL refactors the current design to avoid a copy of them per
isolate, and instead shares them process-wide. Still, we need to free
the allocated heap arrays when the last isolate dies to avoid leaks.
This can probably be refactored later by statically initializing more
and avoiding the heap allocations all together.

This refactoring will also allow us to use {CallInterfaceDescriptor}s
from wasm background compilation threads, which are not bound to any
isolate.

R=mstarzinger@chromium.org, titzer@chromium.org

Bug: v8:6600
Change-Id: If8625b89951eec8fa8986b49a5c166e874a72494
Reviewed-on: https://chromium-review.googlesource.com/1100879
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53803}