Allow to enable sandbox behind a setting and validate it works

[bpasero]

The idea is to eventually enable this by default in insiders.

Things to check:

• 🏃 There are no issues from the contextBridge when using the exposed API from our preload script
• 🏃 Investigate the impact on running as admin when sandbox: true
• 🏃 Performance validation & tuning

[bpasero]

From @deepak1556 on running as admin:

Running the application as elevated on macOS and windows will work, the problematic scenarios are the following,

• On Linux, if a user the installed the application as root technically they should be able to launch the application but the issue would be the sandbox will now run under admin privilege and access to files which are owned by a different user will fail and most often the user data directory would not be owned by root and chrome's internal logic would abort when not being able to read/write to this folder.
• The second scenario on linux is when application was installed as normal user but then tried to launch with sudo, in this case the sandbox which uses execve would fail to stat the executable after launching a process and lead to a hard crash. This makes chrome unable to launch child processes. The decision was then made to never allow running as elevated on linux under sandbox, https://bugs.chromium.org/p/chromium/issues/detail?id=638180
• On Windows, when running the application as elevated while applocker is enabled will cause the sandboxed process to fail launch https://bugs.chromium.org/p/chromium/issues/detail?id=740132

[bpasero]

Test plan item: #155827