Format core.def file.

Wrap many of the lines in the core.def file and make it more consistent
on how it adds annotations vs definitions.

Change-Id: I2f7860833b2022f1a8aaae36b374158e346c7820
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/289177
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Auto-Submit: dan sinclair <dsinclair@chromium.org>
Reviewed-by: James Price <jrprice@google.com>

Author: dj2