chore: enable v2 sandbox on mac

[nornagon]

Description of Change

This re-enables the v2 sandbox on mac (disabled by 878c5b6). That commit asserts that the v2 sandbox would prevent the mixed-sandbox mode from working, but in my testing with this change, it seems to work fine.

$ ps aux | grep Electron | grep type=renderer
# (abridged)
33083 .../Electron Helper --type=renderer [...] --no-sandbox
33082 .../Electron Helper --type=renderer [...] --enable-sandbox --seatbelt-client=53

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant documentation is changed or added
• PR title follows semantic commit guidelines

Release Notes

Notes:

• switch to V2 sandbox on mac

[nornagon]

marking as WIP because this has exposed some failures on linux and some tests that expect the sandbox option to do weird things like loading the sandboxed renderer client without actually sandboxing the renderer.

[codebytere]

ah dangit i didn't intend to approve this yet, ignore the above 🤦‍♀️

unintentional

[nornagon]

Rebased on top of #15894

[deepak1556]

Upstream is trying to remove the kMacV2Sandbox feature flag soon, they tried it in 71 but due to some failures its fortunately delayed 5406108

[nornagon]

Pretty sure I can update & land this before 72. Thanks for the info.

[nornagon]

I believe the mac and arm failures are flakes, see #16027

[deepak1556]

https://github.com/electron/electron/blob/master/patches/common/chromium/mac_fix_form_control_rendering_on_10_14_mojave.patch can be removed.

[release-clerk]

Release Notes Persisted

• switch to V2 sandbox on mac