[PermissionsPolicyForWorkers] Parse SharedWorkerOptions.allow

Parse the allow attribute on SharedWorkerOptions using
PermissionsPolicyParser::ParseAttribute() in SharedWorker::CreateImpl()
when PermissionsPolicyForSharedWorkers is enabled, and log any parser
messages to the execution context console.

This is part of a series of CLs implementing permissions policy for
shared workers behind a feature flag, see the attached tracking bug for
more details.

Change-Id: Ib148b2f6abb98905bae06f28a632fd6575056c0c
Bug: 562705553
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8426409
Reviewed-by: Daniel Vogelheim <vogelheim@chromium.org>
Reviewed-by: Yoshisato Yanagisawa <yyanagisawa@chromium.org>
Commit-Queue: Antonio Sartori <antoniosartori@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1722939}