This patch excludes brand symbols from the result of
JSReceiver::GetPrivateEntries so that the brands do not show up
when the instances are inspected from the DevTools (e.g. via
`Runtime.getProperties()`).

To implement this, we use a bit in the Symbols to denote whether
it's a brand symbol. A brand symbol is also a private name
symbol so that we can just reuse the IC for accessing private
names and do not need to jump through extra ORs.

Design doc: https://docs.google.com/document/d/1N91LObhQexnB0eE7EvGe57HsvNMFX16CaWu-XCTnnmY/edit

Bug: v8:8671, v8:9839, v8:8330
Change-Id: I24346aeedce3602395289052d1e1350ae9390354
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1909757Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Cr-Commit-Position: refs/heads/master@{#64899}