Use naming similar to the spec: "table" instead of "function table",
"element segment" instead of "function table init".

Change-Id: Ib1b6cdfa566f8bd00017ccedf9440084204f10ff
Reviewed-on: https://chromium-review.googlesource.com/c/1273612
Commit-Queue: Ben Smith <binji@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56545}