Bail out if name in proxy is private symbol.
Also, do stack check to avoid deeply nested proxy.

Spec: https://tc39.es/ecma262/#sec-reflect.get
Change-Id: I0761762b074d5af892e8d7e419c87c9bbea99241
Bug: v8:8958
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1682680
Commit-Queue: Z Nguyen-Huu <duongn@microsoft.com>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62747}