This CL adds two new runtime calls for table operations:
  - Runtime_WasmTableInit
  - Runtime_WasmTableCopy

These runtime calls (will) implement the semantics for the corresponding
bytecodes from the bulk memory proposal. The actual implementation
of these runtime calls will be done in further CLs.

The third table operation, table.drop, will be implemented with inline
code, similar to memory.drop. This is also be done in a further CL.

R=mstarzinger@chromium.org
CC=​binji@chromium.org
BUG=v8:7747

Change-Id: I498aa054329baf9f72ae55d245b12c3ccd4157b7
Reviewed-on: https://chromium-review.googlesource.com/c/1408994
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58786}