Rename and reformat all gyp files.  They were previously converted to
gn but not renamed to preserve continuity in git.  This rename completes
the removal of all traces of gyp.

BUG=angleproject:1569

Change-Id: I50123105d8881583184ffc564bed65d9fbe4d41c
Reviewed-on: https://chromium-review.googlesource.com/1187885
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>