Add new `pref` to disable upcoming privacy related Firefox window

[Juraj-Masiar]

Firefox Nightly 143 now shows this:

It would be great if web-ext would disable it by default.

I have seen this: #3176, but this feels reasonable :)

NOTE:
I've tried to use these two locally:

      'termsofuse.acceptedDate=1754040410093',
      'termsofuse.acceptedVersion=4',

But it doesn't help, there is likely something else but I can't find it...

[Rob--W]

Firefox's enterprise policy implementation does something similar, perhaps we can use that logic in web-ext as well? https://searchfox.org/mozilla-central/rev/ce0d41b6033e2a104904327a43edf730245f5241/browser/components/enterprisepolicies/Policies.sys.mjs#2672-2673

[rpl]

The webdriver classic/bidi internals in Firefox use this "termsofuse.bypassNotification" boolean pref to flip this off:

https://searchfox.org/mozilla-central/rev/ce0d41b6033e2a104904327a43edf730245f5241/remote/shared/RecommendedPreferences.sys.mjs#377-378

@Juraj-Masiar setting this pref through web-ext run --pref="..." did bypass the dialog for me on a Nightly build, would you mind to double-check if that works also for you? especially if you are trying this on a release build, that would help to confirm this is the pref that we should set by default also for web-ext run.

[Juraj-Masiar]

Thanks @rpl for the fix!
That alone fixed it for me, even without specifying the other two that I've tried before.

Sadly I can't test it on release since I don't have it installed. I'm only using ESR and Nightly for development.
But I'll test it on Beta once it reaches it.