Rename DedicatedOrSharedWorkerFetchContext to ...GlobalScopeContext

As a part of the work for https://crbug.com/40364838, rename
(Web)DedicatedOrSharedWorkerFetchContext to
(Web)DedicatedOrSharedWorkerGlobalScopeContext. This is in preparation
for adding the ability for the class to create a ServiceWorkerProvider.

Bug: 40364838
Change-Id: I9820bae209134eb5f8e0da8ef97ef8314a6ad8be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6580404
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Liang Zhao <lzhao@microsoft.com>
Commit-Queue: Dave Risney <david.risney@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1466734}