Current implementation of built in function lookup uses
autogenerated switch statements. Instead, use the perfect
hash mapping to have the lookup use arrays instead. This
will improve runtime performance.

Bug: angleproject:3805
Change-Id: I6d0ba62d79abd53a7fe818fe675282800781f256
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1756883
Commit-Queue: Clemen Deng <clemendeng@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>