Gosub Browser Progress, pt51

Test-fitted the process-isolation poc into the main branch. It seems to work, but there are still some smaller details that the poc didn't address that we need to fix. We'll get there.

One thing that the security system caught: there were some seccomp filters missing, mostly because i've tested everything with local names, which didn't need a DNS lookup. Now, that we are testing with real domains, all of a sudden I was missing some functionality. So annoying to debug, but props to the system to actually guard against unapproved system calls :-)

I'm doing some research on the Manifest v2 vs v3. Complicated stuff, but I think we can deal with some of the v3 issues that keep adblockers awake at night. I have some preliminary documentation stored at https://gist.github.com/jaytaph/6dcb382e5f4d40ed577ba9dad9b1c838 until we can make this more official. (we're no where near this point, but still good to think about things).