Use a constexpr array for es3 copy conversion table. With the relaxed C++14 constexpr rules allowed in Chromium, we can use a constexpr sorted array to store our table data. This can lead to very fast lookups while being more maintanable than using auto- generator scripts for every lookup table. Note that to be sure this syntax is permitted, we should land this through the bots and let it sit for a little while. Bug: angleproject:1389 Change-Id: I9395c40276470108ce3e5786d8f1b8d85462c517 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/777544 Commit-Queue: Jamie Madill <jmadill@google.com> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>