Previously array sizes were calculated as the OR of all flag and enum
masks, equal to 2^(number of bits used for flags and enums) - 1, which
could be less than the actual needed array size.

This fix moves array size calculation to the autogen script and changes
the size to one more than the maximum potential value.

Bug: angleproject:3524
Change-Id: Ia4eb2a83fc7deea84e18958efcda8b57632035f9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1655954
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>