./wpt run should find browsers on macOS

[gsnedders]

Currently, ./wpt run just looks in $PATH (or %PATH% on Windows); on macOS, browsers are almost always installed in /Applications or $HOME/Applications and we should search these too.

[foolip]

@youennf maybe you know how one would go about this?

[gsnedders]

I think we just need a list of paths to check in /Applications and $HOME/Applications? I'm pretty sure there isn't a better way of doing this than hardcoding those paths and hardcoding a list of Application bundle names (like we already do for firefox, etc., on Linux), though that probably mean parsing the Info.plist to get the actual binary path which is a bit of a pain (Python 2's plistlib only supports the XML serialisation) though given we only need to do this on macOS we should be able to rely on the psutil tool to convert them to XML and then parse them.

[qiuzhong]

@gsnedders , PR #9806 was submitted to fix this and had been merged long ago. Can we close this issue now?

[gsnedders]

Yeah, this works for most browsers now.