Create an IWA specific keyed service factory

This CL adds the IsolatedWebAppBrowserContextServiceFactory that allows
developers to register keyed services only if the browser context
supports isolated web apps. In a first step, it ports the
MultiCaptureUsageIndicatorServiceFactory to this new factory type.

Bug: 438148719
Change-Id: I059ceef85973aba920663505396fe9f74f2c33eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6840577
Auto-Submit: Simon Hangl <simonha@google.com>
Commit-Queue: Simon Hangl <simonha@google.com>
Reviewed-by: Andrew Rayskiy <greengrape@google.com>
Cr-Commit-Position: refs/heads/main@{#1502729}