This patch merges ClassLiteralProperty::PUBLIC_FIELD and
ClassLiteralProperty::PRIVATE_FIELD into ClassLiteralProperty::FIELD,
and moves the visibility part into ClassLiteralProperty::is_private()
for the ease of adding new combinations in the future.

Bug: v8:8330

R=gsathya@chromium.org

Change-Id: I54f64d05bccb1867d9111e4c80158a6075406d80
Reviewed-on: https://chromium-review.googlesource.com/c/1291052Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Cr-Commit-Position: refs/heads/master@{#56910}